iOS底层系列之＜45＞--内存管理＜1＞NSProxy的使用

1、定时器无法释放问题

当使用定时器的时候，下面的情况，定时器是无法释放的

#import "TimeVC.h"
#import "Temp.h"
#import "JHProxy.h"@interface TimeVC ()
@property (strong, nonatomic) CADisplayLink *link;
@property (strong, nonatomic) NSTimer *timer;
@end@implementation TimeVC- (void)viewDidLoad {[super viewDidLoad];self.link = [CADisplayLink displayLinkWithTarget:self selector:@selector(linkTest)];[self.link addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];self.timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(timerTest) userInfo:nil repeats:YES];
}- (void)timerTest {NSLog(@"%s",__func__);
}- (void)linkTest {NSLog(@"%s",__func__);
}- (void)dealloc {[self.link invalidate];self.link = nil;[self.timer invalidate];self.timer = nil;NSLog(@"%s",__func__);
}@end

内存无法释放原因分析：

解决方案：搞一个中间类，弱引用控制器

2、内存释放方法一

写一个中间类

#import NS_ASSUME_NONNULL_BEGIN@interface Temp : NSObject
@property (weak, nonatomic) id target;
+ (id)proxyWithTarget:(id)target;
@endNS_ASSUME_NONNULL_END

实现消息转发

#import "Temp.h"@implementation Temp
+ (instancetype)proxyWithTarget:(id)target {Temp *tempProxy = [[Temp alloc] init];tempProxy.target = target;return tempProxy;
}- (id)forwardingTargetForSelector:(SEL)aSelector {return self.target;
}
@end

调用方法：

- (void)viewDidLoad {[super viewDidLoad];self.link = [CADisplayLink displayLinkWithTarget:[Temp proxyWithTarget:self] selector:@selector(linkTest)];[self.link addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];self.timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:[Temp proxyWithTarget:self] selector:@selector(timerTest) userInfo:nil repeats:YES];
}

3、内存释放方法一

使用NSProxy类，代理类，天生就是用来做代理的类

#import NS_ASSUME_NONNULL_BEGIN@interface JHProxy : NSProxy
@property (weak, nonatomic) id target;
+ (id)proxyWithTarget:(id)target;
@endNS_ASSUME_NONNULL_END

#import "JHProxy.h"@implementation JHProxy
+ (instancetype)proxyWithTarget:(id)target {JHProxy *tempProxy = [JHProxy alloc];tempProxy.target = target;return tempProxy;
}- (NSMethodSignature *)methodSignatureForSelector:(SEL)sel {return [self.target methodSignatureForSelector:sel];
}- (void)forwardInvocation:(NSInvocation *)invocation {[invocation invokeWithTarget:self.target];
}@end

调用方法：

- (void)viewDidLoad {[super viewDidLoad];self.link = [CADisplayLink displayLinkWithTarget:[JHProxy proxyWithTarget:self] selector:@selector(linkTest)];[self.link addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];self.timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:[JHProxy proxyWithTarget:self] selector:@selector(timerTest) userInfo:nil repeats:YES];
}

总结：尽量使用NSProxy，因为它的功能就是用来消息转发的，不会有第一阶段和第二阶段（参考消息转发机制3大阶段）

4. Swift

Swift中用不了NSProxy

class WeakProxy: NSObject {weak var target: NSObjectProtocol?var sel: Selector?public required init(target:NSObjectProtocol?, sel: Selector?) {self.target = targetself.sel = selsuper.init()guard target?.responds(to: sel) == true else {return}let method = class_getInstanceMethod(self.classForCoder, #selector(WeakTimerProxy.redirectionMethod))!class_replaceMethod(self.classForCoder, sel!, method_getImplementation(method), method_getTypeEncoding(method))}@objc func redirectionMethod() {if self.target != nil {self.target?.perform(self.sel)}}
}

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