// ModalViewController.h
#import <UIKit/UIKit.h>
@interface ModalViewController : UIViewController
@end
// ModalViewController.m
#import "ModalViewController.h"
@interface ModalViewController ()
@property (nonatomic ,strong) void(^block)();
@end
@implementation ModalViewController
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
[self dismissViewControllerAnimated:YES completion:nil];
}
- (void)dealloc
{
NSLog(@"%@对象销毁",self);
}
/**
* 说明,如果_block里面保存的代码只是在主线程执行，而且内部保存的代码用到外界的self
那么,必须得__weak typeof(self) weakSelf = self;然后用weakSelf变量就可以了，
放在循环引用,
如果保存的代码还得在子线程或者主线程延时之后做一些操作的话，还得用到self的话，首先第一步是
__weak typeof(self) weakSelf = self;第二步在保存的代码位置写__strong typeof(weakSelf) strongSelf = weakSelf;然后用strongSelf变量就可以了
*/
- (void)viewDidLoad {
[super viewDidLoad];
int a = 0;
// Block循环引用,跟block调用没有关系
// block只要访问外部强指针对象变量,就会对这个变量进行强引用.
__weak typeof(self) weakSelf = self;
_block = ^{
__strong typeof(weakSelf) strongSelf = weakSelf;
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2* NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
NSLog(@"延迟打印%@",strongSelf);
});
};
_block();
}
@end
// ViewController.h
#import <UIKit/UIKit.h>
@interface ViewController : UIViewController
@end
// ViewController.m
#import "ViewController.h"
#import "ModalViewController.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
ModalViewController *modalVc = [[ModalViewController alloc] init];
modalVc.view.backgroundColor = [UIColor redColor];
[self presentViewController:modalVc animated:YES completion:nil];
}
- (void)viewDidLoad {
[super viewDidLoad];
}
@end
