优化新旧设备判断逻辑。Review by 硬币。

@@ -69,6 +69,7 @@ static int const kOpenUDIDRedundancySlots = 100;
 static NSString * const kYohoSecretInfo = @"com.yoho.buy.secretinfo";
 static NSString * const kYohoBuyUdid = @"com.yoho.buy.udid";
 
+static BOOL isNew = YES;
 static NSString * const kYohoDeviceInfo = @"com.yoho.buy.deviceinfo";
 static NSString * const kYohoBuyUsedDevice = @"com.yoho.buy.useddevice";
 
@@ -397,12 +398,9 @@ static NSString * const kYohoBuyUsedDevice = @"com.yoho.buy.useddevice";
 
 + (void) setUsedDevice
 {
-    NSMutableDictionary *yohoinfoKVPairs = (NSMutableDictionary *)[YH_KeychainStore load:kYohoDeviceInfo];
-    if (yohoinfoKVPairs == nil) {
-        yohoinfoKVPairs = [NSMutableDictionary dictionary];
-    }
-    
-    if (![yohoinfoKVPairs[kYohoBuyUsedDevice] isEqualToString:@"Y"]) {
+    if ([self isNewDevice]) {
+        isNew = NO;
+        NSMutableDictionary *yohoinfoKVPairs = [NSMutableDictionary dictionary];
         [yohoinfoKVPairs setObject:@"Y" forKey:kYohoBuyUsedDevice];
         [YH_KeychainStore save:kYohoDeviceInfo data:yohoinfoKVPairs];
     }
@@ -410,18 +408,15 @@ static NSString * const kYohoBuyUsedDevice = @"com.yoho.buy.useddevice";
 
 + (BOOL) isNewDevice
 {
-    static BOOL isNew = YES;
-    if (isNew == NO) {
-        return NO;
-    }
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
+        NSMutableDictionary *yohoinfoKVPairs = (NSMutableDictionary *)[YH_KeychainStore load:kYohoDeviceInfo];
+        if (yohoinfoKVPairs && yohoinfoKVPairs[kYohoBuyUsedDevice]) {
+            isNew = NO;
+        }
+    });
     
-    NSMutableDictionary *yohoinfoKVPairs = (NSMutableDictionary *)[YH_KeychainStore load:kYohoDeviceInfo];
-    if (yohoinfoKVPairs == nil || yohoinfoKVPairs[kYohoBuyUsedDevice] == nil) {
-        return YES;
-    } else {
-        isNew = NO;
-        return NO;
-    }
+    return isNew;
 }
 
 @end