$ 問題拋出來
1.所有自定義方法的
block都需要__weak嗎?
2.凡是,block內帶self的都需要__weak嗎?
3.凡是, 系統方法中的block, 都不需要__weak嗎?
看看上述問題的反問語氣, 相必語文過關的同學們都知道答案,一看就是 No No No ~
-> ?? 恭喜你~ right !
$ but why ?
至于原因 ??
想必大伙都知道, 互相strong持有成了一個環 , 然后就無法釋放了~
$ block 常見場景(暫時想到的一些情況, 后續想到繼續補充)
first, code準備:
?? 一個子View -- TestOneView, 創建各種參數為block的方法
// TestOneView.h
#import <UIKit/UIKit.h>
typedef void(^ZYOneBlock1)();
typedef void(^ZYOneBlock2)();
@interface TestOneView : UIView
// copy修飾
@property (nonatomic, copy) ZYOneBlock1 oneBlock;
// weak修飾
@property (nonatomic, weak) ZYOneBlock1 weak_oneBlock;
// 持有 傳入的block , 但是 weak
- (void)testWeakBlock:(ZYOneBlock1) block;
// 不持有 傳入的block , 在method中直接執行掉
- (void)testBlock2WithBlock:(ZYOneBlock2) secondblock;
@end
// TestOneView.m
#import "TestOneView.h"
@implementation TestOneView
/*
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect {
// Drawing code
}
*/
// 持有 傳入的block , strong
-(void)setOneBlock:(ZYOneBlock1)oneBlock{
_oneBlock = oneBlock;
_oneBlock();
}
// 持有 傳入的block , 但是 weak
- (void)testWeakBlock:(ZYOneBlock1) block;
{
self.weak_oneBlock = block;
}
// 不持有 傳入的block , 在method中直接執行掉
- (void)testBlock2WithBlock:(ZYOneBlock2) secondblock;
{
secondblock();
}
// 通過dealloc 檢測能否釋放
-(void)dealloc{
NSLog(@"%s",__func__);
}
@end
go on ~ , code一個被push的VC -- TestOneViewController , 即是 block縱橫所在的江湖
?????? block 出場 ??????
-
<1> A 操作 B的bloc
(1).傳給子View的block被子view ??
strong持有 , block塊中使用了_ivar(成員變量) 、strong property , 處理方式如下:- (void)testStrongBlock_1{ [self.view addSubview: self.oneView]; __weak typeof(self) weakSelf = self; self.oneView.oneBlock = ^{ __strong typeof(weakSelf) strongSelf = weakSelf; strongSelf->_intType = 11; strongSelf.pArray = @[@(11)]; }; }(2).傳入的block塊中 含有本類的實例方法
- (void)testMethod_StrongBlock_1{ [self.view addSubview: self.oneView]; __weak typeof(self) weakSelf = self; self.oneView.oneBlock = ^{ __strong typeof(weakSelf) strongSelf = weakSelf; // method [strongSelf containSelfMethod]; }; } - (void)containSelfMethod{ _intType = 1010; self.pArray = @[@(2020)]; }(3).傳給子view的block 被子view ??
weak持有, 在方法內被執行完。無需weakSelf- (void)testWeakBlock_1{ [self.view addSubview: self.oneView]; [self.oneView testWeakBlock:^{ _intType = 111; self.pArray = @[@(1)]; }]; }(4).傳給子view的block ?不 被子view 持有, 直接執行掉。
無需weakSelf- (void)testParamBlock_2{ [self.view addSubview: self.oneView]; [self.oneView testBlock2WithBlock:^{ _intType = 22; self.pArray = @[@(1)]; }]; } -
<2> A 操作 A的block
(a).block作參數, ?不 被持有
- (void)testParam_SelfBlock_1{ [self testParam_SelfBlcokWith:^(NSArray * arr) { self.pArray = arr; NSLog(@"%s",__func__); }]; } - (void)testParam_SelfBlcokWith:(MyBlockOne)myBlock{ NSArray * arr = @[@"myblock1"]; myBlock(arr); }(b).block作參數, ??被持有
- (void)testCopy_SelfBlock_1{ __weak typeof(self) weakSelf = self; [self testCopy_SelfBlcokWith:^(NSArray * arr) { __strong typeof(weakSelf) strongSelf = weakSelf; strongSelf.pArray = arr; NSLog(@"%s",__func__); }]; } - (void)testCopy_SelfBlcokWith:(MyBlockOne)myBlock{ self.myBlock1 = myBlock; NSArray * arr = @[@"myblock1"]; NSLog(@"%s",__func__); sleep(1); NSLog(@"%s",__func__); self.myBlock1(arr); } -
<3> GCD的block(系統的)
無需weakSelf。注意: GCD延時block, 會使VC pop后延遲釋放- (void)didMoveToParentViewController:(UIViewController *)parent{ [self.oneView removeFromSuperview]; NSLog(@"%s , %@",__func__ ,self); dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{ NSLog(@"%s , %@",__func__ ,self); [self testBackTimerAfter]; // 點擊pop 時,會延遲2s dealloc }); } - (void)testBackTimerAfter{ [self.oneView testWeakBlock:^{ NSLog(@"%s , %@",__func__ ,self); }]; __weak typeof(self) weakSelf = self; _oneView.oneBlock = ^{ __strong typeof(weakSelf) strongSelf = weakSelf; NSLog(@"%s , %@",__func__ ,strongSelf); }; } -
<4> ?補充?, 對于NSTimer addTarget: self...
_weak typeof(self) weakSelf = self; _timer = [NSTimer scheduledTimerWithTimeInterval:3.0f target:weakSelf selector:@selector(timerFire:) userInfo:nil repeats:YES];對于如上解決方式, 是有誤的,詳解 可參考 ?? 解決NSTimer/CADisplayLink的循環引用
超懶人 點擊 github demo 下載 調試 。
祝愿有所收獲哦 ~ _ ~
