perfromSelector 的非延遲方法
- (id)performSelector:(SEL)aSelector;
- (id)performSelector:(SEL)aSelector withObject:(id)object;
- (id)performSelector:(SEL)aSelector withObject:(id)object1 withObject:(id)object2;
底層實現(xiàn) 源碼地址
- (id)performSelector:(SEL)sel {
if (!sel) [self doesNotRecognizeSelector:sel];
return ((id(*)(id, SEL))objc_msgSend)(self, sel);
}
- (id)performSelector:(SEL)sel withObject:(id)obj {
if (!sel) [self doesNotRecognizeSelector:sel];
return ((id(*)(id, SEL, id))objc_msgSend)(self, sel, obj);
}
- (id)performSelector:(SEL)sel withObject:(id)obj1 withObject:(id)obj2 {
if (!sel) [self doesNotRecognizeSelector:sel];
return ((id(*)(id, SEL, id, id))objc_msgSend)(self, sel, obj1, obj2);
}
performSelector是運行時系統(tǒng)負責去找方法,在編譯時不會對調(diào)用的方法做檢查,只有在運行的時候才會檢查,如果方法存在就調(diào)用,如果放不存在就不會調(diào)用。當然也可以通過使用 - (BOOL)respondsToSelector:(SEL)aSelector;方法去判斷對象是否實現(xiàn)了要調(diào)用的方法。
這三個方法調(diào)用都是直接執(zhí)行,相當于直接通過對象調(diào)用方法, [self performSelector:@selector(test)];與[self test]; 執(zhí)行的結(jié)果是一致的,通過這些方法去執(zhí)行是不需要子線程去啟動Runloop的。方法內(nèi)運行的線程就是調(diào)用performSelector所在的線程
- (void)viewDidLoad {
[super viewDidLoad];
NSLog(@"當前線程:%@",[NSThread currentThread]);
[self performSelector:@selector(test1)];
[self performSelector:@selector(test2:) withObject:@"小明"];
[self performSelector:@selector(test3:andAge:) withObject:@"小明" withObject:@"10"];
NSLog(@"****************************************");
dispatch_queue_t queue = dispatch_queue_create("新的并發(fā)隊列", DISPATCH_QUEUE_CONCURRENT);
dispatch_async(queue, ^{
NSLog(@"當前線程:%@",[NSThread currentThread]);
[self performSelector:@selector(test1)];
[self performSelector:@selector(test2:) withObject:@"小明"];
[self performSelector:@selector(test3:andAge:) withObject:@"小明" withObject:@"10"];
});
}
-(void)test1{
NSLog(@"執(zhí)行了test1 當前線程:%@",[NSThread currentThread]);
}
-(void)test2:(NSString *)name{
NSLog(@"執(zhí)行了test2 name:%@ 當前線程:%@",name,[NSThread currentThread]);
}
-(void)test3:(NSString *)name andAge:(NSString *) age{
NSLog(@"執(zhí)行了test3 name:%@ age:%@ 當前線程:%@",name,age,[NSThread currentThread]);
}
/*輸出
當前線程:<NSThread: 0x600000624a80>{number = 1, name = main}
執(zhí)行了test1 當前線程:<NSThread: 0x600000624a80>{number = 1, name = main}
執(zhí)行了test2 name:小明 當前線程:<NSThread: 0x600000624a80>{number = 1, name = main}
執(zhí)行了test3 name:小明 age:10 當前線程:<NSThread: 0x600000624a80>{number = 1, name = main}
****************************************
當前線程:<NSThread: 0x60000066d380>{number = 6, name = (null)}
執(zhí)行了test1 當前線程:<NSThread: 0x60000066d380>{number = 6, name = (null)}
執(zhí)行了test2 name:小明 當前線程:<NSThread: 0x60000066d380>{number = 6, name = (null)}
執(zhí)行了test3 name:小明 age:10 當前線程:<NSThread: 0x60000066d380>{number = 6, name = (null)}
*/
上面的方法,最多可以支持傳遞2個參數(shù),如果要傳遞2個以上,上面的方法就不能使用了。
- 方法一 objc_msgSend
((void (*) (id, SEL, NSString *, NSString *, NSString *)) objc_msgSend) (self, @selector(test4:andAge:andSex:), @"小明", @"10", @"男");
-(void)test4:(NSString *)name andAge:(NSString *) age andSex:(NSString *)sex{
NSLog(@"執(zhí)行了test4 name:%@ age:%@ sex:%@ 當前線程:%@",name,age,sex,[NSThread currentThread]);
}
/*輸出
執(zhí)行了test4 name:小明 age:10 sex:男 當前線程:<NSThread: 0x600000a68580>{number = 1, name = main}
*/
-
方法二 NSInvocation
//1、方法簽名 NSMethodSignature *signature = [[self class]instanceMethodSignatureForSelector:@selector(test4:andAge:andSex:)]; //包裝方法 NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:signature]; //方法調(diào)用者 invocation.target = self; //要調(diào)用的方法和方法簽名中的方法一樣 invocation.selector = @selector(test4:andAge:andSex:); NSString *name = @"小明"; NSString *age = @"10"; NSString *sex = @"男"; //設(shè)置傳遞的參數(shù) 0 代表target 1代表 selector 所以從2開始 [invocation setArgument:&name atIndex:2]; [invocation setArgument:&age atIndex:3]; [invocation setArgument:&sex atIndex:4]; //執(zhí)行方法 [invocation invoke]; //獲取返回值 NSString *returnValue = @""; [invocation getReturnValue:&returnValue]; NSLog(@"返回值:%@",returnValue); -(NSString *)test4:(NSString *)name andAge:(NSString *) age andSex:(NSString *)sex{ NSLog(@"執(zhí)行了test4 name:%@ age:%@ sex:%@ 當前線程:%@",name,age,sex,[NSThread currentThread]); return @"這是返回值"; } /* 執(zhí)行了test4 name:小明 age:10 sex:男 當前線程:<NSThread: 0x600000f9c980>{number = 1, name = main} 返回值:這是返回值 */
performSelector 的延遲執(zhí)行方法
- (void)performSelector:(SEL)aSelector withObject:(nullable id)anArgument afterDelay:(NSTimeInterval)delay inModes:(NSArray<NSRunLoopMode> *)modes;
- (void)performSelector:(SEL)aSelector withObject:(nullable id)anArgument afterDelay:(NSTimeInterval)delay;
在蘋果文檔中的介紹:
這個方法是設(shè)置了一個timer,在當前線程的runloop上執(zhí)行aSelector消息,這個計時器的默認模式是NSDefaultRunLoopMode。當計時器觸發(fā)時,會嘗試從runloop中取出消息行,如果runloop運行的模式是NSDefaultRunLoopMode,那么就會執(zhí)行它,如果當前runloop是其他模式,則會等待runloop處于NSDefaultRunLoopMode在運行。
如果希望在運行循環(huán)處于NSDefaultRunLoopMode以外的其他模式時使消息出隊,請改用performSelector:withObject:afterDelay:inModes:方法。如果不確定當前線程是否為主線程,則可以使用performSelectorOnMainThread:withObject:waitUntilDone:或performSelectorOnMainThread:withObject:waitUntilDone:modes:方法來確保選擇器在主線程上執(zhí)行。要取消排隊的消息,請使用cancelPreviousPerformRequestsWithTarget:或cancelPreviousPerformRequestsWithTarget:selector:object:方法。
特別注意事項
此方法向其當前上下文的runloop進行注冊,并依賴于runloop才能正確執(zhí)行。一種常見情況是,當在 dispatch queue上調(diào)用這個方法,但是runloop并沒有啟動,這個方法是不會運行的。如果想使用這個延遲功能在dispatch queue上,則應使用dispatch_after和相關(guān)方法來獲得所需的行為。
- 在主線程中調(diào)用
-(void)test1:(NSString *)name{
NSLog(@"執(zhí)行了test1 name:%@ 當前線程:%@",name,[NSThread currentThread]);
}
- (void)viewDidLoad {
[super viewDidLoad];
//在主線程中,它的runloop是默認開啟的,所有下面的方法是可以直接執(zhí)行
[self performSelector:@selector(test1:) withObject:@"小明" afterDelay:2];
}
//輸出
//執(zhí)行了test1 name:小明 當前線程:<NSThread: 0x6000012a8b00>{number = 1, name = main}
- 在隊列中,不調(diào)用[[NSRunLoop currentRunLoop] run];
- (void)viewDidLoad {
[super viewDidLoad];
dispatch_queue_t queue = dispatch_queue_create("并發(fā)隊列", DISPATCH_QUEUE_CONCURRENT);
dispatch_async(queue, ^{
//這個方法是不會執(zhí)行的,因為此時的這個線程的runloop默認是沒有開啟的
[self performSelector:@selector(test1:) withObject:@"小紅" afterDelay:2];
});
}
- 在隊列中,在調(diào)用performSelector之前調(diào)用[[NSRunLoop currentRunLoop] run];
- (void)viewDidLoad {
[super viewDidLoad];
dispatch_queue_t queue = dispatch_queue_create("并發(fā)隊列", DISPATCH_QUEUE_CONCURRENT);
dispatch_async(queue, ^{
[[NSRunLoop currentRunLoop] run];
//這個方法是不會執(zhí)行的,調(diào)用run方法只是嘗試開啟當前線程中的runloop,但是如果該線程中并沒有任何事件(source、timer、observer)的話,runloop并不會開啟。
[self performSelector:@selector(test1:) withObject:@"小紅" afterDelay:1];
});
}
- 在隊列中,在調(diào)用performSelector之后調(diào)用[[NSRunLoop currentRunLoop] run];
-(void)viewDidLoad {
[super viewDidLoad];
dispatch_queue_t queue = dispatch_queue_create("并發(fā)隊列", DISPATCH_QUEUE_CONCURRENT);
dispatch_async(queue, ^{
//成功調(diào)用函數(shù)
[self performSelector:@selector(test1:) withObject:@"小紅" afterDelay:1];
[[NSRunLoop currentRunLoop] run];
});
}
//輸出
//執(zhí)行了test1 name:小紅 當前線程:<NSThread: 0x6000015b0a00>{number = 7, name = (null)}