Converted <MASConstraint> protocol to abstract class (to support proper code completion in Xcode)

@@ -97,7 +97,7 @@
 
     int padding = invertedInsets ? 100 : self.padding;
     UIEdgeInsets paddingInsets = UIEdgeInsetsMake(padding, padding, padding, padding);
-    for (id<MASConstraint> constraint in self.animatableConstraints) {
+    for (MASConstraint *constraint in self.animatableConstraints) {
         constraint.insets = paddingInsets;
     }
 

@@ -11,6 +11,9 @@
          location = "group:MASConstraint.h">
       </FileRef>
       <FileRef
+         location = "group:MASConstraint.m">
+      </FileRef>
+      <FileRef
          location = "group:MASCompositeConstraint.h">
       </FileRef>
       <FileRef

@@ -11,9 +11,8 @@
 
 /**
  *	A group of MASConstraint objects
- *  conforms to MASConstraint
  */
-@interface MASCompositeConstraint : NSObject <MASConstraint>
+@interface MASCompositeConstraint : MASConstraint
 
 /**
  *	Creates a composite with a predefined array of children

@@ -17,15 +17,12 @@
 
 @implementation MASCompositeConstraint
 
-@synthesize delegate = _delegate;
-@synthesize updateExisting = _updateExisting;
-
 - (id)initWithChildren:(NSArray *)children {
     self = [super init];
     if (!self) return nil;
 
     _childConstraints = [children mutableCopy];
-    for (id<MASConstraint> constraint in _childConstraints) {
+    for (MASConstraint *constraint in _childConstraints) {
         constraint.delegate = self;
     }
 
@@ -34,7 +31,7 @@
 
 #pragma mark - MASConstraintDelegate
 
-- (void)constraint:(id<MASConstraint>)constraint shouldBeReplacedWithConstraint:(id<MASConstraint>)replacementConstraint {
+- (void)constraint:(MASConstraint *)constraint shouldBeReplacedWithConstraint:(MASConstraint *)replacementConstraint {
     NSUInteger index = [self.childConstraints indexOfObject:constraint];
     NSAssert(index != NSNotFound, @"Could not find constraint %@", constraint);
     [self.childConstraints replaceObjectAtIndex:index withObject:replacementConstraint];
@@ -42,28 +39,28 @@
 
 #pragma mark - NSLayoutConstraint constant proxies
 
-- (id<MASConstraint> (^)(MASEdgeInsets))insets {
+- (MASConstraint * (^)(MASEdgeInsets))insets {
     return ^id(MASEdgeInsets insets) {
         self.insets = insets;
         return self;
     };
 }
 
-- (id<MASConstraint> (^)(CGFloat))offset {
+- (MASConstraint * (^)(CGFloat))offset {
     return ^id(CGFloat offset) {
         self.offset = offset;
         return self;
     };
 }
 
-- (id<MASConstraint> (^)(CGSize))sizeOffset {
+- (MASConstraint * (^)(CGSize))sizeOffset {
     return ^id(CGSize offset) {
         self.sizeOffset = offset;
         return self;
     };
 }
 
-- (id<MASConstraint> (^)(CGPoint))centerOffset {
+- (MASConstraint * (^)(CGPoint))centerOffset {
     return ^id(CGPoint offset) {
         self.centerOffset = offset;
         return self;
@@ -72,18 +69,18 @@
 
 #pragma mark - NSLayoutConstraint multiplier proxies 
 
-- (id<MASConstraint> (^)(CGFloat))multipliedBy {
+- (MASConstraint * (^)(CGFloat))multipliedBy {
     return ^id(CGFloat multiplier) {
-        for (id<MASConstraint> constraint in self.childConstraints) {
+        for (MASConstraint *constraint in self.childConstraints) {
             constraint.multipliedBy(multiplier);
         }
         return self;
     };
 }
 
-- (id<MASConstraint> (^)(CGFloat))dividedBy {
+- (MASConstraint * (^)(CGFloat))dividedBy {
     return ^id(CGFloat divider) {
-        for (id<MASConstraint> constraint in self.childConstraints) {
+        for (MASConstraint *constraint in self.childConstraints) {
             constraint.dividedBy(divider);
         }
         return self;
@@ -92,30 +89,30 @@
 
 #pragma mark - MASLayoutPriority proxies
 
-- (id<MASConstraint> (^)(MASLayoutPriority))priority {
+- (MASConstraint * (^)(MASLayoutPriority))priority {
     return ^id(MASLayoutPriority priority) {
-        for (id<MASConstraint> constraint in self.childConstraints) {
+        for (MASConstraint *constraint in self.childConstraints) {
             constraint.priority(priority);
         }
         return self;
     };
 }
 
-- (id<MASConstraint> (^)())priorityLow {
+- (MASConstraint * (^)())priorityLow {
     return ^id{
         self.priority(MASLayoutPriorityDefaultLow);
         return self;
     };
 }
 
-- (id<MASConstraint> (^)())priorityMedium {
+- (MASConstraint * (^)())priorityMedium {
     return ^id{
         self.priority(MASLayoutPriorityDefaultMedium);
         return self;
     };
 }
 
-- (id<MASConstraint> (^)())priorityHigh {
+- (MASConstraint * (^)())priorityHigh {
     return ^id{
         self.priority(MASLayoutPriorityDefaultHigh);
         return self;
@@ -124,27 +121,27 @@
 
 #pragma mark - NSLayoutRelation proxies
 
-- (id<MASConstraint> (^)(id))equalTo {
+- (MASConstraint * (^)(id))equalTo {
     return ^id(id attr) {
-        for (id<MASConstraint> constraint in self.childConstraints.copy) {
+        for (MASConstraint *constraint in self.childConstraints.copy) {
             constraint.equalTo(attr);
         }
         return self;
     };
 }
 
-- (id<MASConstraint> (^)(id))greaterThanOrEqualTo {
+- (MASConstraint * (^)(id))greaterThanOrEqualTo {
     return ^id(id attr) {
-        for (id<MASConstraint> constraint in self.childConstraints.copy) {
+        for (MASConstraint *constraint in self.childConstraints.copy) {
             constraint.greaterThanOrEqualTo(attr);
         }
         return self;
     };
 }
 
-- (id<MASConstraint> (^)(id))lessThanOrEqualTo {
+- (MASConstraint * (^)(id))lessThanOrEqualTo {
     return ^id(id attr) {
-        for (id<MASConstraint> constraint in self.childConstraints.copy) {
+        for (MASConstraint *constraint in self.childConstraints.copy) {
             constraint.lessThanOrEqualTo(attr);
         }
         return self;
@@ -153,7 +150,7 @@
 
 #pragma mark - Semantic properties
 
-- (id<MASConstraint>)with {
+- (MASConstraint *)with {
     return self;
 }
 
@@ -161,8 +158,8 @@
 
 #if TARGET_OS_MAC && !TARGET_OS_IPHONE
 
-- (id<MASConstraint>)animator {
-    for (id<MASConstraint> constraint in self.childConstraints) {
+- (MASConstraint *)animator {
+    for (MASConstraint *constraint in self.childConstraints) {
         [constraint animator];
     }
     return self;
@@ -172,11 +169,11 @@
 
 #pragma mark - debug helpers
 
-- (id<MASConstraint> (^)(id))key {
+- (MASConstraint * (^)(id))key {
     return ^id(id key) {
         self.mas_key = key;
         int i = 0;
-        for (id<MASConstraint> constraint in self.childConstraints) {
+        for (MASConstraint *constraint in self.childConstraints) {
             constraint.key([NSString stringWithFormat:@"%@[%d]", key, i++]);
         }
         return self;
@@ -186,25 +183,25 @@
 #pragma mark - NSLayoutConstraint constant setters
 
 - (void)setInsets:(MASEdgeInsets)insets {
-    for (id<MASConstraint> constraint in self.childConstraints) {
+    for (MASConstraint *constraint in self.childConstraints) {
         constraint.insets = insets;
     }
 }
 
 - (void)setOffset:(CGFloat)offset {
-    for (id<MASConstraint> constraint in self.childConstraints) {
+    for (MASConstraint *constraint in self.childConstraints) {
         constraint.offset = offset;
     }
 }
 
 - (void)setSizeOffset:(CGSize)sizeOffset {
-    for (id<MASConstraint> constraint in self.childConstraints) {
+    for (MASConstraint *constraint in self.childConstraints) {
         constraint.sizeOffset = sizeOffset;
     }
 }
 
 - (void)setCenterOffset:(CGPoint)centerOffset {
-    for (id<MASConstraint> constraint in self.childConstraints) {
+    for (MASConstraint *constraint in self.childConstraints) {
         constraint.centerOffset = centerOffset;
     }
 }
@@ -212,14 +209,14 @@
 #pragma mark - MASConstraint
 
 - (void)install {
-    for (id<MASConstraint> constraint in self.childConstraints) {
+    for (MASConstraint *constraint in self.childConstraints) {
         constraint.updateExisting = self.updateExisting;
         [constraint install];
     }
 }
 
 - (void)uninstall {
-    for (id<MASConstraint> constraint in self.childConstraints) {
+    for (MASConstraint *constraint in self.childConstraints) {
         [constraint uninstall];
     }
 }

@@ -15,7 +15,7 @@
  *  Constraint can represent single NSLayoutConstraint (MASViewConstraint) 
  *  or a group of NSLayoutConstraints (MASComposisteConstraint)
  */
-@protocol MASConstraint <NSObject>
+@interface MASConstraint : NSObject
 
 // Chaining Support
 
@@ -24,56 +24,56 @@
  *  only affects MASConstraints in which the first item's NSLayoutAttribute is one of the following 
  *  NSLayoutAttributeTop, NSLayoutAttributeLeft, NSLayoutAttributeBottom, NSLayoutAttributeRight
  */
-- (id<MASConstraint> (^)(MASEdgeInsets insets))insets;
+- (MASConstraint * (^)(MASEdgeInsets insets))insets;
 
 /**
  *	Modifies the NSLayoutConstraint constant,
  *  only affects MASConstraints in which the first item's NSLayoutAttribute is one of the following
  *  NSLayoutAttributeWidth, NSLayoutAttributeHeight
  */
-- (id<MASConstraint> (^)(CGSize offset))sizeOffset;
+- (MASConstraint * (^)(CGSize offset))sizeOffset;
 
 /**
  *	Modifies the NSLayoutConstraint constant,
  *  only affects MASConstraints in which the first item's NSLayoutAttribute is one of the following
  *  NSLayoutAttributeCenterX, NSLayoutAttributeCenterY
  */
-- (id<MASConstraint> (^)(CGPoint offset))centerOffset;
+- (MASConstraint * (^)(CGPoint offset))centerOffset;
 
 /**
  *	Modifies the NSLayoutConstraint constant
  */
-- (id<MASConstraint> (^)(CGFloat offset))offset;
+- (MASConstraint * (^)(CGFloat offset))offset;
 
 /**
  *	Sets the NSLayoutConstraint multiplier property
  */
-- (id<MASConstraint> (^)(CGFloat multiplier))multipliedBy;
+- (MASConstraint * (^)(CGFloat multiplier))multipliedBy;
 
 /**
  *	Sets the NSLayoutConstraint multiplier to 1.0/dividedBy
  */
-- (id<MASConstraint> (^)(CGFloat divider))dividedBy;
+- (MASConstraint * (^)(CGFloat divider))dividedBy;
 
 /**
  *	Sets the NSLayoutConstraint priority to a float or MASLayoutPriority
  */
-- (id<MASConstraint> (^)(MASLayoutPriority priority))priority;
+- (MASConstraint * (^)(MASLayoutPriority priority))priority;
 
 /**
  *	Sets the NSLayoutConstraint priority to MASLayoutPriorityLow
  */
-- (id<MASConstraint> (^)())priorityLow;
+- (MASConstraint * (^)())priorityLow;
 
 /**
  *	Sets the NSLayoutConstraint priority to MASLayoutPriorityMedium
  */
-- (id<MASConstraint> (^)())priorityMedium;
+- (MASConstraint * (^)())priorityMedium;
 
 /**
  *	Sets the NSLayoutConstraint priority to MASLayoutPriorityHigh
  */
-- (id<MASConstraint> (^)())priorityHigh;
+- (MASConstraint * (^)())priorityHigh;
 
 /**
  *	Sets the constraint relation to NSLayoutRelationEqual
@@ -81,7 +81,7 @@
  *    MASViewAttribute, UIView, NSNumber, NSArray
  *  see readme for more details.
  */
-- (id<MASConstraint> (^)(id attr))equalTo;
+- (MASConstraint * (^)(id attr))equalTo;
 
 /**
  *	Sets the constraint relation to NSLayoutRelationGreaterThanOrEqual
@@ -89,7 +89,7 @@
  *    MASViewAttribute, UIView, NSNumber, NSArray
  *  see readme for more details.
  */
-- (id<MASConstraint> (^)(id attr))greaterThanOrEqualTo;
+- (MASConstraint * (^)(id attr))greaterThanOrEqualTo;
 
 /**
  *	Sets the constraint relation to NSLayoutRelationLessThanOrEqual
@@ -97,17 +97,17 @@
  *    MASViewAttribute, UIView, NSNumber, NSArray
  *  see readme for more details.
  */
-- (id<MASConstraint> (^)(id attr))lessThanOrEqualTo;
+- (MASConstraint * (^)(id attr))lessThanOrEqualTo;
 
 /**
  *	optional semantic property which has no effect but improves the readability of constraint
  */
-- (id<MASConstraint>)with;
+- (MASConstraint *)with;
 
 /**
  *	Sets the constraint debug name
  */
-- (id<MASConstraint> (^)(id key))key;
+- (MASConstraint * (^)(id key))key;
 
 
 // NSLayoutConstraint constant Setters
@@ -146,7 +146,7 @@
 /**
  *  Whether or not to go through the animator proxy when modifying the constraint
  */
-@property (nonatomic, copy, readonly) id<MASConstraint> animator;
+@property (nonatomic, copy, readonly) MASConstraint *animator;
 #endif
 
 /**
@@ -177,6 +177,6 @@
  *	Notifies the delegate when the constraint needs to be replaced with another constraint. For example 
  *  A MASViewConstraint may turn into a MASCompositeConstraint when an array is passed to one of the equality blocks
  */
-- (void)constraint:(id<MASConstraint>)constraint shouldBeReplacedWithConstraint:(id<MASConstraint>)replacementConstraint;
+- (void)constraint:(MASConstraint *)constraint shouldBeReplacedWithConstraint:(MASConstraint *)replacementConstraint;
 
 @end

+//
+//  MASConstraint.m
+//  Masonry
+//
+//  Created by Nick Tymchenko on 1/20/14.
+//
+
+#import "MASConstraint.h"
+
+#define methodNotImplemented() \
+    @throw [NSException exceptionWithName:NSInternalInconsistencyException \
+                                   reason:[NSString stringWithFormat:@"You must override %@ in a subclass.", NSStringFromSelector(_cmd)] \
+                                 userInfo:nil]
+
+@implementation MASConstraint
+
+#pragma mark - Init
+
+- (id)init {
+	NSAssert(![self isMemberOfClass:[MASConstraint class]], @"MASConstraint is an abstract class, you should not instantiate it directly.");
+	return [super init];
+}
+
+#pragma mark - Abstract
+
+- (MASConstraint * (^)(MASEdgeInsets insets))insets { methodNotImplemented(); }
+
+- (MASConstraint * (^)(CGSize offset))sizeOffset { methodNotImplemented(); }
+
+- (MASConstraint * (^)(CGPoint offset))centerOffset { methodNotImplemented(); }
+
+- (MASConstraint * (^)(CGFloat offset))offset { methodNotImplemented(); }
+
+- (MASConstraint * (^)(CGFloat multiplier))multipliedBy { methodNotImplemented(); }
+
+- (MASConstraint * (^)(CGFloat divider))dividedBy { methodNotImplemented(); }
+
+- (MASConstraint * (^)(MASLayoutPriority priority))priority { methodNotImplemented(); }
+
+- (MASConstraint * (^)())priorityLow { methodNotImplemented(); }
+
+- (MASConstraint * (^)())priorityMedium { methodNotImplemented(); }
+
+- (MASConstraint * (^)())priorityHigh { methodNotImplemented(); }
+
+- (MASConstraint * (^)(id attr))equalTo { methodNotImplemented(); }
+
+- (MASConstraint * (^)(id attr))greaterThanOrEqualTo { methodNotImplemented(); }
+
+- (MASConstraint * (^)(id attr))lessThanOrEqualTo { methodNotImplemented(); }
+
+- (MASConstraint *)with { methodNotImplemented(); }
+
+- (MASConstraint * (^)(id key))key { methodNotImplemented(); }
+
+- (void)setInsets:(MASEdgeInsets)insets { methodNotImplemented(); }
+
+- (void)setSizeOffset:(CGSize)sizeOffset { methodNotImplemented(); }
+
+- (void)setCenterOffset:(CGPoint)centerOffset { methodNotImplemented(); }
+
+- (void)setOffset:(CGFloat)offset { methodNotImplemented(); }
+
+#if TARGET_OS_MAC && !TARGET_OS_IPHONE
+
+- (MASConstraint *)animator { methodNotImplemented(); }
+
+#endif
+
+- (void)install { methodNotImplemented(); }
+
+- (void)uninstall { methodNotImplemented(); }
+
+@end

@@ -20,38 +20,38 @@
  *	The following properties return a new MASViewConstraint
  *  with the first item set to the makers associated view and the appropriate MASViewAttribute
  */
-@property (nonatomic, strong, readonly) id<MASConstraint> left;
-@property (nonatomic, strong, readonly) id<MASConstraint> top;
-@property (nonatomic, strong, readonly) id<MASConstraint> right;
-@property (nonatomic, strong, readonly) id<MASConstraint> bottom;
-@property (nonatomic, strong, readonly) id<MASConstraint> leading;
-@property (nonatomic, strong, readonly) id<MASConstraint> trailing;
-@property (nonatomic, strong, readonly) id<MASConstraint> width;
-@property (nonatomic, strong, readonly) id<MASConstraint> height;
-@property (nonatomic, strong, readonly) id<MASConstraint> centerX;
-@property (nonatomic, strong, readonly) id<MASConstraint> centerY;
-@property (nonatomic, strong, readonly) id<MASConstraint> baseline;
+@property (nonatomic, strong, readonly) MASConstraint *left;
+@property (nonatomic, strong, readonly) MASConstraint *top;
+@property (nonatomic, strong, readonly) MASConstraint *right;
+@property (nonatomic, strong, readonly) MASConstraint *bottom;
+@property (nonatomic, strong, readonly) MASConstraint *leading;
+@property (nonatomic, strong, readonly) MASConstraint *trailing;
+@property (nonatomic, strong, readonly) MASConstraint *width;
+@property (nonatomic, strong, readonly) MASConstraint *height;
+@property (nonatomic, strong, readonly) MASConstraint *centerX;
+@property (nonatomic, strong, readonly) MASConstraint *centerY;
+@property (nonatomic, strong, readonly) MASConstraint *baseline;
 
 /**
  *	Creates a MASCompositeConstraint with type MASCompositeConstraintTypeEdges
  *  which generates the appropriate MASViewConstraint children (top, left, bottom, right)
  *  with the first item set to the makers associated view
  */
-@property (nonatomic, strong, readonly) id<MASConstraint> edges;
+@property (nonatomic, strong, readonly) MASConstraint *edges;
 
 /**
  *	Creates a MASCompositeConstraint with type MASCompositeConstraintTypeSize
  *  which generates the appropriate MASViewConstraint children (width, height)
  *  with the first item set to the makers associated view
  */
-@property (nonatomic, strong, readonly) id<MASConstraint> size;
+@property (nonatomic, strong, readonly) MASConstraint *size;
 
 /**
  *	Creates a MASCompositeConstraint with type MASCompositeConstraintTypeCenter
  *  which generates the appropriate MASViewConstraint children (centerX, centerY)
  *  with the first item set to the makers associated view
  */
-@property (nonatomic, strong, readonly) id<MASConstraint> center;
+@property (nonatomic, strong, readonly) MASConstraint *center;
 
 /**
  *  Whether or not to check for an existing constraint instead of adding constraint

@@ -33,7 +33,7 @@
 
 - (NSArray *)install {
     NSArray *constraints = self.constraints.copy;
-    for (id<MASConstraint> constraint in constraints) {
+    for (MASConstraint *constraint in constraints) {
         constraint.updateExisting = self.updateExisting;
         [constraint install];
     }
@@ -43,7 +43,7 @@
 
 #pragma mark - MASConstraintDelegate
 
-- (void)constraint:(id<MASConstraint>)constraint shouldBeReplacedWithConstraint:(id<MASConstraint>)replacementConstraint {
+- (void)constraint:(MASConstraint *)constraint shouldBeReplacedWithConstraint:(MASConstraint *)replacementConstraint {
     NSUInteger index = [self.constraints indexOfObject:constraint];
     NSAssert(index != NSNotFound, @"Could not find constraint %@", constraint);
     [self.constraints replaceObjectAtIndex:index withObject:replacementConstraint];
@@ -51,7 +51,7 @@
 
 #pragma mark - constraint properties
 
-- (id<MASConstraint>)addConstraintWithLayoutAttribute:(NSLayoutAttribute)layoutAttribute {
+- (MASConstraint *)addConstraintWithLayoutAttribute:(NSLayoutAttribute)layoutAttribute {
     MASViewAttribute *viewAttribute = [[MASViewAttribute alloc] initWithView:self.view layoutAttribute:layoutAttribute];
     MASViewConstraint *constraint = [[MASViewConstraint alloc] initWithFirstViewAttribute:viewAttribute];
     constraint.delegate = self;
@@ -61,54 +61,54 @@
 
 #pragma mark - standard Attributes
 
-- (id<MASConstraint>)left {
+- (MASConstraint *)left {
     return [self addConstraintWithLayoutAttribute:NSLayoutAttributeLeft];
 }
 
-- (id<MASConstraint>)top {
+- (MASConstraint *)top {
     return [self addConstraintWithLayoutAttribute:NSLayoutAttributeTop];
 }
 
-- (id<MASConstraint>)right {
+- (MASConstraint *)right {
     return [self addConstraintWithLayoutAttribute:NSLayoutAttributeRight];
 }
 
-- (id<MASConstraint>)bottom {
+- (MASConstraint *)bottom {
     return [self addConstraintWithLayoutAttribute:NSLayoutAttributeBottom];
 }
 
-- (id<MASConstraint>)leading {
+- (MASConstraint *)leading {
     return [self addConstraintWithLayoutAttribute:NSLayoutAttributeLeading];
 }
 
-- (id<MASConstraint>)trailing {
+- (MASConstraint *)trailing {
     return [self addConstraintWithLayoutAttribute:NSLayoutAttributeTrailing];
 }
 
-- (id<MASConstraint>)width {
+- (MASConstraint *)width {
     return [self addConstraintWithLayoutAttribute:NSLayoutAttributeWidth];
 }
 
-- (id<MASConstraint>)height {
+- (MASConstraint *)height {
     return [self addConstraintWithLayoutAttribute:NSLayoutAttributeHeight];
 }
 
-- (id<MASConstraint>)centerX {
+- (MASConstraint *)centerX {
     return [self addConstraintWithLayoutAttribute:NSLayoutAttributeCenterX];
 }
 
-- (id<MASConstraint>)centerY {
+- (MASConstraint *)centerY {
     return [self addConstraintWithLayoutAttribute:NSLayoutAttributeCenterY];
 }
 
-- (id<MASConstraint>)baseline {
+- (MASConstraint *)baseline {
     return [self addConstraintWithLayoutAttribute:NSLayoutAttributeBaseline];
 }
 
 
 #pragma mark - composite Attributes
 
-- (id<MASConstraint>)edges {
+- (MASConstraint *)edges {
     NSArray *children = @[
         [[MASViewConstraint alloc] initWithFirstViewAttribute:self.view.mas_top],
         [[MASViewConstraint alloc] initWithFirstViewAttribute:self.view.mas_left],
@@ -121,7 +121,7 @@
     return constraint;
 }
 
-- (id<MASConstraint>)size {
+- (MASConstraint *)size {
     NSArray *children = @[
         [[MASViewConstraint alloc] initWithFirstViewAttribute:self.view.mas_width],
         [[MASViewConstraint alloc] initWithFirstViewAttribute:self.view.mas_height]
@@ -132,7 +132,7 @@
     return constraint;
 }
 
-- (id<MASConstraint>)center {
+- (MASConstraint *)center {
     NSArray *children = @[
         [[MASViewConstraint alloc] initWithFirstViewAttribute:self.view.mas_centerX],
         [[MASViewConstraint alloc] initWithFirstViewAttribute:self.view.mas_centerY]

@@ -13,9 +13,8 @@
 /**
  *  A single constraint.
  *  Contains the attributes neccessary for creating a NSLayoutConstraint and adding it to the appropriate view
- *  conforms to MASConstraint
  */
-@interface MASViewConstraint : NSObject <MASConstraint, NSCopying>
+@interface MASViewConstraint : MASConstraint <NSCopying>
 
 /**
  *	First item/view and first attribute of the NSLayoutConstraint

@@ -28,9 +28,6 @@
 
 @implementation MASViewConstraint
 
-@synthesize delegate = _delegate;
-@synthesize updateExisting = _updateExisting;
-
 - (id)initWithFirstViewAttribute:(MASViewAttribute *)firstViewAttribute {
     self = [super init];
     if (!self) return nil;
@@ -93,28 +90,28 @@
 
 #pragma mark - NSLayoutConstraint constant proxies
 
-- (id<MASConstraint> (^)(MASEdgeInsets))insets {
+- (MASConstraint * (^)(MASEdgeInsets))insets {
     return ^id(MASEdgeInsets insets){
         self.insets = insets;
         return self;
     };
 }
 
-- (id<MASConstraint> (^)(CGSize))sizeOffset {
+- (MASConstraint * (^)(CGSize))sizeOffset {
     return ^id(CGSize offset) {
         self.sizeOffset = offset;
         return self;
     };
 }
 
-- (id<MASConstraint> (^)(CGPoint))centerOffset {
+- (MASConstraint * (^)(CGPoint))centerOffset {
     return ^id(CGPoint offset) {
         self.centerOffset = offset;
         return self;
     };
 }
 
-- (id<MASConstraint> (^)(CGFloat))offset {
+- (MASConstraint * (^)(CGFloat))offset {
     return ^id(CGFloat offset){
         self.offset = offset;
         return self;
@@ -123,7 +120,7 @@
 
 #pragma mark - NSLayoutConstraint multiplier proxies
 
-- (id<MASConstraint> (^)(CGFloat))multipliedBy {
+- (MASConstraint * (^)(CGFloat))multipliedBy {
     return ^id(CGFloat multiplier) {
         NSAssert(!self.hasBeenInstalled,
                  @"Cannot modify constraint multiplier after it has been installed");
@@ -134,7 +131,7 @@
 }
 
 
-- (id<MASConstraint> (^)(CGFloat))dividedBy {
+- (MASConstraint * (^)(CGFloat))dividedBy {
     return ^id(CGFloat divider) {
         NSAssert(!self.hasBeenInstalled,
                  @"Cannot modify constraint multiplier after it has been installed");
@@ -146,7 +143,7 @@
 
 #pragma mark - MASLayoutPriority proxies
 
-- (id<MASConstraint> (^)(MASLayoutPriority))priority {
+- (MASConstraint * (^)(MASLayoutPriority))priority {
     return ^id(MASLayoutPriority priority) {
         NSAssert(!self.hasBeenInstalled,
                  @"Cannot modify constraint priority after it has been installed");
@@ -156,21 +153,21 @@
     };
 }
 
-- (id<MASConstraint> (^)())priorityLow {
+- (MASConstraint * (^)())priorityLow {
     return ^id{
         self.priority(MASLayoutPriorityDefaultLow);
         return self;
     };
 }
 
-- (id<MASConstraint> (^)())priorityMedium {
+- (MASConstraint * (^)())priorityMedium {
     return ^id{
         self.priority(MASLayoutPriorityDefaultMedium);
         return self;
     };
 }
 
-- (id<MASConstraint> (^)())priorityHigh {
+- (MASConstraint * (^)())priorityHigh {
     return ^id{
         self.priority(MASLayoutPriorityDefaultHigh);
         return self;
@@ -179,7 +176,7 @@
 
 #pragma mark - NSLayoutRelation proxies
 
-- (id<MASConstraint> (^)(id))equalityWithRelation:(NSLayoutRelation)relation {
+- (MASConstraint * (^)(id))equalityWithRelation:(NSLayoutRelation)relation {
     return ^id(id attribute) {
         if ([attribute isKindOfClass:NSArray.class]) {
             NSAssert(!self.hasLayoutRelation, @"Redefinition of constraint relation");
@@ -203,21 +200,21 @@
     };
 }
 
-- (id<MASConstraint> (^)(id))equalTo {
+- (MASConstraint * (^)(id))equalTo {
     return [self equalityWithRelation:NSLayoutRelationEqual];
 }
 
-- (id<MASConstraint> (^)(id))greaterThanOrEqualTo {
+- (MASConstraint * (^)(id))greaterThanOrEqualTo {
     return [self equalityWithRelation:NSLayoutRelationGreaterThanOrEqual];
 }
 
-- (id<MASConstraint> (^)(id))lessThanOrEqualTo {
+- (MASConstraint * (^)(id))lessThanOrEqualTo {
     return [self equalityWithRelation:NSLayoutRelationLessThanOrEqual];
 }
 
 #pragma mark - Semantic properties
 
-- (id<MASConstraint>)with {
+- (MASConstraint *)with {
     return self;
 }
 
@@ -225,7 +222,7 @@
 
 #if TARGET_OS_MAC && !TARGET_OS_IPHONE
 
-- (id<MASConstraint>)animator {
+- (MASConstraint *)animator {
     self.useAnimator = YES;
     return self;
 }
@@ -234,7 +231,7 @@
 
 #pragma mark - debug helpers
 
-- (id<MASConstraint> (^)(id))key {
+- (MASConstraint * (^)(id))key {
     return ^id(id key) {
         self.mas_key = key;
         return self;

@@ -19,7 +19,7 @@
     return self;
 }
 
-- (void)constraint:(id<MASConstraint>)constraint shouldBeReplacedWithConstraint:(id<MASConstraint>)replacementConstraint {
+- (void)constraint:(MASConstraint *)constraint shouldBeReplacedWithConstraint:(MASConstraint *)replacementConstraint {
     [self.constraints replaceObjectAtIndex:[self.constraints indexOfObject:constraint] withObject:replacementConstraint];
 }
 

@@ -40,7 +40,7 @@ SpecBegin(MASConstraintMaker) {
 }
 
 - (void)testCreateCenterYAndCenterXChildren {
-    composite = maker.center;
+    composite = (MASCompositeConstraint *)maker.center;
 
     expect(composite.childConstraints).to.haveCountOf(2);
 
@@ -55,7 +55,7 @@ SpecBegin(MASConstraintMaker) {
 
 - (void)testCreateAllEdges {
     MAS_VIEW *newView = MAS_VIEW.new;
-    composite = maker.edges;
+    composite = (MASCompositeConstraint *)maker.edges;
     composite.equalTo(newView);
 
     expect(composite.childConstraints).to.haveCountOf(4);
@@ -82,7 +82,7 @@ SpecBegin(MASConstraintMaker) {
 }
 
 - (void)testCreateWidthAndHeightChildren {
-    composite = maker.size;
+    composite = (MASCompositeConstraint *)maker.size;
     expect(composite.childConstraints).to.haveCountOf(2);
 
     MASViewConstraint *viewConstraint = composite.childConstraints[0];