Cadisplaylink, nstimer circular reference solution

Preface ：CADisplayLink、NSTimer Circular quotation problem
​CADisplayLink、NSTimer Would be right Target Generate strong quotes , If target They are strongly quoted again , Then it will trigger a circular reference .

  
 
 

   
  
  
@interface ViewController ()
   
  
  
@property (nonatomic, strong) CADisplayLink *link;
   
  
  
@property (nonatomic, strong) NSTimer *time;
   
  
  
@end
   
  
  
@implementation ViewController
   
  
  
- (void)viewDidLoad {
   
  
  
 [super viewDidLoad];
   
  
  
 //  Ensure the calling frequency and frame brushing frequency  60fps
   
  
  
 self.link = [CADisplayLink displayLinkWithTarget:self selector:@selector(linkTest)];
   
  
  
 [self.link addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode] ;
   
  
  
 
   
  
  
 self.time = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(timeTest) userInfo:nil repeats:YES]; 
   
  
  
}
   
  
  
- (void)timeTest {
   
  
  
 NSLog(@"%s", __func__);
   
  
  
}
   
  
  
- (void)linkTest {
   
  
  
 NSLog(@"%s", __func__);
   
  
  
}
   
  
  
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
   
  
  
 NSLog(@"%s", __func__);
   
  
  
 [self.time invalidate];
   
  
  
}
  
 
 

__weak typeof(self) weakSelf = self; Can we solve it NSTimer The problem of circular quotation ？
answer ： We cannot pass __weak typeof(self) weakSelf = self; Code to solve circular references .
__weak typeof(self) weakSelf = self; It's for block Can solve the problem of circular reference .
When
Scheme 1 、 Use NSTimer Use block（CADisplayLink Not provided block api You can't use ）
​NSTime Use to provide block Of API , adopt __weak Solve the problem of sequential reference

  
 
 

   
  
  
- (void)viewDidLoad {
   
  
  
 [super viewDidLoad];
   
  
  
 
   
  
  
 __weak typeof(self) weakSelf = self;
   
  
  
 self.time = [NSTimer scheduledTimerWithTimeInterval:1.0 repeats:YES block:^(NSTimer * _Nonnull timer) {
   
  
  
 [weakSelf timeTest];
   
  
  
 } ];
   
  
  
}
   
  
  
- (void)timeTest {
   
  
  
 NSLog(@"%s", __func__);
   
  
  
}
   
  
  
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
   
  
  
 NSLog(@"%s", __func__);
   
  
  
 [self.time invalidate];
   
  
  
}
  
 
 

Option two 、 Use NSObject forward
​ Through intermediate variables , It is a reference in the middle that becomes a weak reference .
​ First step ： Create inheritance NSObject Of RHMiddleTarget Intermediate document , establish target attribute , Use weak To modify by weak reference

  
 
 

   
  
  
#import <Foundation/Foundation.h>
   
  
  
@interface RHMiddleTarget : NSObject
   
  
  
@property (nonatomic, weak) id target;
   
  
  
+ (instancetype)middleTargetWithTarget:(id)target;
   
  
  
@end
   
  
  

   
  
  
#import "RHMiddleTarget.h"
   
  
  
@implementation RHMiddleTarget
   
  
  
+ (instancetype)middleTargetWithTarget:(id)target {
   
  
  
 RHMiddleTarget *middleTarget = [[RHMiddleTarget alloc] init];
   
  
  
 middleTarget.target = target;
   
  
  
 return middleTarget;
   
  
  
}
   
  
  
- (id)forwardingTargetForSelector:(SEL)aSelector {
   
  
  
 //  Return the object that can be processed ,  Send... To the object aSelector news 
   
  
  
 // objc_msgSend(self.target, aSelector);
   
  
  
 return self.target;
   
  
  
}
   
  
  
@end
  
 
 

The second step ： In the use of CADisplayLink and NSTimer Medium target Pass it to the intermediate variable ：

  
 
 

   
  
  
//  Ensure the calling frequency and frame brushing frequency  60fps
   
  
  
 self.link = [CADisplayLink displayLinkWithTarget:[RHMiddleTarget middleTargetWithTarget:self] selector:@selector(linkTest)];
   
  
  
 [self.link addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode] ;
   
  
  
 
   
  
  
 self.time = [NSTimer scheduledTimerWithTimeInterval:1.0 target:[RHMiddleTarget middleTargetWithTarget:self] selector:@selector(timeTest) userInfo:nil repeats:YES];
  
 
 

The third step ： Test verification ：

  
 
 

   
  
  
2022-07-05 16:01:47.895716+0800 Interview03- Timer [10828:260303] -[ViewController timeTest]
   
  
  
2022-07-05 16:01:48.895649+0800 Interview03- Timer [10828:260303] -[ViewController timeTest]
   
  
  
2022-07-05 16:01:49.895571+0800 Interview03- Timer [10828:260303] -[ViewController timeTest]
   
  
  
2022-07-05 16:01:50.666056+0800 Interview03- Timer [10828:260303] -[ViewController touchesBegan:withEvent:]
  
 
 

Option three 、 Use NSProxy forward
First step ： Create inheritance NSObject Of RHMiddleTarget Intermediate document , establish target attribute , Use weak To modify by weak reference

  
 
 

   
  
  
#import <Foundation/Foundation.h>
   
  
  
@interface RHMiddleTarget : NSProxy
   
  
  
@property (nonatomic, weak) id target;
   
  
  
+ (instancetype)middleTargetWithTarget:(id)target;
   
  
  
@end
   
  
  
#import "RHMiddleTarget.h"
   
  
  
@implementation RHMiddleTarget
   
  
  
+ (instancetype)middleTargetWithTarget:(id)target {
   
  
  
 RHMiddleTarget *middleTarget = [RHMiddleTarget alloc];
   
  
  
 middleTarget.target = target;
   
  
  
 return middleTarget;
   
  
  
}
   
  
  
//  Return method signature 
   
  
  
- (NSMethodSignature *)methodSignatureForSelector:(SEL)sel {
   
  
  
 return [self.target methodSignatureForSelector:sel];
   
  
  
}
   
  
  
//  Make the corresponding call 
   
  
  
- (void)forwardInvocation:(NSInvocation *)invocation {
   
  
  
 [invocation invokeWithTarget:self.target];
   
  
  
}
  
 
 

The second step ： In the use of CADisplayLink and NSTimer Medium target Pass it to the intermediate variable

  
 
 

   
  
  
//  Ensure the calling frequency and frame brushing frequency  60fps
   
  
  
 self.link = [CADisplayLink displayLinkWithTarget:[RHMiddleTarget middleTargetWithTarget:self] selector:@selector(linkTest)];
   
  
  
 [self.link addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode] ;
   
  
  
 
   
  
  
 self.time = [NSTimer scheduledTimerWithTimeInterval:1.0 target:[RHMiddleTarget middleTargetWithTarget:self] selector:@selector(timeTest) userInfo:nil repeats:YES];
  
 
 

The third step ： Test verification

  
 
 

   
  
  
2022-07-05 16:27:25.427454+0800 Interview03- Timer [11550:281823] -[ViewController linkTest]
   
  
  
2022-07-05 16:27:25.444101+0800 Interview03- Timer [11550:281823] -[ViewController linkTest]
   
  
  
2022-07-05 16:27:25.456983+0800 Interview03- Timer [11550:281823] -[ViewController touchesBegan:withEvent:]
  
 
 

Option four 、 Use viewWillDisappear
​ When the controller is destroyed or the timer stops , Call the following method

  
 
 

   
  
  
[self.timer invalidate];
   
  
  
 [self.link invalidate];
   
  
  
 self.timer = nil;
   
  
  
 self.link = nil;