第一種情況直接weak修飾后初始化劲适，編譯器會(huì)提示警告：Assigning retained object to weak property; object will be released after assignment，賦值后會(huì)被釋放

#import "ViewController.h"

@interface ViewController ()

@property (nonatomic, weak) UIView *bview;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    self.view.backgroundColor = [UIColor whiteColor];
    self.bview = [[UIView alloc] init];
    NSLog(@"%@",self.bview);
}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    NSLog(@"點(diǎn)擊屏幕后%@",self.bview);
}

@end

結(jié)果

2023-11-29 10:32:51.003871+0800 OCDemo[82234:2684446] (null)
2023-11-29 10:33:01.251990+0800 OCDemo[82234:2684446] 點(diǎn)擊屏幕后(null)

第二種情況用weak修飾賦值

#import "ViewController.h"

@interface ViewController ()

@property (nonatomic, weak) UIView *bview;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    self.view.backgroundColor = [UIColor whiteColor];
    UIView *tempView = [[UIView alloc] init];
    self.bview = tempView;
    NSLog(@"%@",self.bview);
}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    NSLog(@"點(diǎn)擊屏幕后%@",self.bview);
}

2023-11-29 10:36:17.927977+0800 OCDemo[82441:2688402] <UIView: 0x7f81ac704240; frame = (0 0; 0 0); layer = <CALayer: 0x600000a78340>>
2023-11-29 10:36:30.112701+0800 OCDemo[82441:2688402] 點(diǎn)擊屏幕后(null)

第三種情況用weak修飾賦值后添加到view上

#import "ViewController.h"

@interface ViewController ()

@property (nonatomic, weak) UIView *bview;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    self.view.backgroundColor = [UIColor whiteColor];
    UIView *tempView = [[UIView alloc] init];
    self.bview = tempView;
    [self.view addSubview:self.bview];
    NSLog(@"%@",self.bview);
}

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    NSLog(@"點(diǎn)擊屏幕后%@",self.bview);
}

2023-11-29 10:38:46.851065+0800 OCDemo[82679:2691860] <UIView: 0x7faec2f0c010; frame = (0 0; 0 0); layer = <CALayer: 0x6000000ab800>>
2023-11-29 10:38:48.487691+0800 OCDemo[82679:2691860] 點(diǎn)擊屏幕后<UIView: 0x7faec2f0c010; frame = (0 0; 0 0); layer = <CALayer: 0x6000000ab800>>

最后一種情況為啥不被釋放呢，原因是當(dāng)我們執(zhí)行了addSubview:方法之后，后面的視圖就會(huì)被放到這個(gè)subViews數(shù)組里，可以看到，這個(gè)數(shù)組使用copy修飾的，也就是說孙技，這是強(qiáng)引用！正是這個(gè)原因排作，我們才能用weak來修飾一個(gè)控件牵啦。因此可以保持這個(gè)控件的引用計(jì)數(shù)不為0，就不會(huì)被釋放掉了妄痪。

@property(nonatomic,readonly,copy) NSArray<__kindof UIView *> *subviews;

總結(jié)一下：一般情況用weak哈雏，strong都可以的，但是特殊的種情況如果創(chuàng)建一個(gè)view用weak修飾拌夏，沒有add到其他view上僧著，那這個(gè)view就沒有和別的view有強(qiáng)引用關(guān)系，引用計(jì)數(shù)也沒有+1障簿，所以會(huì)被釋放盹愚，反之換成strong修飾的話，它本身就引用計(jì)數(shù)+1了站故，不管有沒有被add到其他view上都不會(huì)被釋放皆怕，所以不想這么糾結(jié)就都用strong修飾吧

還有個(gè)問題解釋一下，strong修飾本身引用計(jì)數(shù)+1西篓，addSubView后又+1愈腾，雖然引用計(jì)數(shù)為2，但是當(dāng)整個(gè)父視圖被銷毀的時(shí)候岂津，這兩個(gè)引用計(jì)數(shù)都會(huì)變成0虱黄，所以不會(huì)造成內(nèi)存泄漏。