Break the strong reference cycle between CADisplayLink and TOMSMorphi…

…ngLabel. CADisplayLink retains the object set as its target and TOMSMorphingLabel references the display link strongly. This gives a strong reference cycle and TOMSMorphingLabel is never deallocated. This commit adds a helper class named TOMSMorphingLabelWeakWrapper which holds a weak reference to the label and forwards necessary messages to it. This breaks the reference cycle and allows deallocating the label. Note that if the weak wrapper's label reference gets nullified due to the label being deallocated, the display link would continue firing its events to the weak wrapper. So it is necessary to properly invalidate the display link in the TOMSMorphingLabel's dealloc.
Austinate · Nov 22, 2014 · d181a01 · d181a01
1 parent 3bb1a66
commit d181a01
Showing 1 changed file with 62 additions and 8 deletions.
diff --git a/Classes/TOMSMorphingLabel.m b/Classes/TOMSMorphingLabel.m
@@ -12,6 +12,18 @@
 
 #define kTOMSKernFactorAttributeName @"kTOMSKernFactorAttributeName"
 
+/** A helper class which is used to break the strong reference cycle
+ *  between CADisplayLink and TOMSMorphingLabel. Does nothing significant,
+ *  just forwards all messages to its morphingLabel property.
+ */
+@interface TOMSMorphingLabelWeakWrapper : NSObject
+@property (nonatomic, weak, readonly) TOMSMorphingLabel *morphingLabel;
+
+- (instancetype)initWithLabel:(TOMSMorphingLabel *)label;
+
+@end
+
+
 @interface TOMSMorphingLabel (){
     void (^_setTextCompletionBlock)(void);
 }
@@ -78,16 +90,20 @@ - (void)designatedInitialization
     _morphingEnabled = YES;
     self.animating = NO;
 
-    self.displayLink = [CADisplayLink displayLinkWithTarget:self
-                                                   selector:@selector(tickInitial)];
-    [self.displayLink addToRunLoop:[NSRunLoop currentRunLoop]
-                           forMode:NSRunLoopCommonModes];
+    [self setupDisplayLinkWithSelector:@selector(tickInitial)];
 
     self.animationDuration = 0.37;
     self.characterAnimationOffset = 0.25;
     self.characterShrinkFactor = 4;
 }
 
+
+- (void)dealloc
+{
+    [_displayLink invalidate];
+    _displayLink = nil;
+}
+
 #pragma mark - Setters
 
 - (void)numberOfAttributionStagesShouldChange
@@ -144,16 +160,27 @@ - (void)tickInitial
         self.displayLink.paused = YES;
         CFTimeInterval duration = self.displayLink.duration;
 
-        self.displayLink = [CADisplayLink displayLinkWithTarget:self
-                                                           selector:@selector(tickMorphing)];
-        [self.displayLink addToRunLoop:[NSRunLoop currentRunLoop]
-                               forMode:NSRunLoopCommonModes];
+        [self setupDisplayLinkWithSelector: @selector(tickMorphing)];
         self.displayLink.paused = YES;
 
         self.displayLinkDuration = duration;
     }
 }
 
+
+- (void)setupDisplayLinkWithSelector:(SEL)selector
+{
+    TOMSMorphingLabelWeakWrapper *displayLinkTarget = [[TOMSMorphingLabelWeakWrapper alloc] initWithLabel:self];
+    CADisplayLink *displayLink = [CADisplayLink displayLinkWithTarget:displayLinkTarget
+                                                             selector:selector];
+
+    [displayLink addToRunLoop:[NSRunLoop currentRunLoop]
+                      forMode:NSRunLoopCommonModes];
+
+    [self.displayLink invalidate];
+    self.displayLink = displayLink;
+}
+
 #pragma mark - Getters
 
 - (CGFloat)easedValue:(CGFloat)p
@@ -431,3 +458,30 @@ - (void)tickMorphing
 }
 
 @end
+
+
+@implementation TOMSMorphingLabelWeakWrapper
+
+- (instancetype)initWithLabel:(TOMSMorphingLabel *)label
+{
+    self = [super init];
+
+    if (self) {
+        _morphingLabel = label;
+    }
+
+    return self;
+}
+
+- (void)tickInitial
+{
+    [self.morphingLabel tickInitial];
+}
+
+- (void)tickMorphing
+{
+    [self.morphingLabel tickMorphing];
+}
+
+@end
+