block与GCD--40：块的循环引用
使用block时，很容易导致“保留环”
- 第一种
#import <Foundation/Foundation.h>
typedef void(^dosomethingBlock)(NSDictionary *dic);
@interface Student : NSObject
- (void)startBlock:(dosomethingBlock)block;
- (void)callBackData;
@end
#import "Student.h"
@interface Student()
@property (nonatomic,copy) dosomethingBlock block;
@end
@implementation Student
- (void)startBlock:(dosomethingBlock)block{
if (block) {
_block = block;
}
}
- (void)callBackData{
if (_block) {
_block(@{@"key":@"value"});
}
}
- (void)dealloc{
NSLog(@"%s",__func__);
}
@end
---------------------
#import "ViewController.h"
#import "Student.h"
@interface ViewController ()
@property (nonatomic,strong) Student *stu;
@property (nonatomic,strong) NSDictionary *dic;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
_stu = [[Student alloc]init];
[_stu startBlock:^(NSDictionary *dic) {
_dic = dic;
NSLog(@"%@",self.dic[@"key"]);
}];
[_stu callBackData];
}
@end运行程序发现student的delloc不会执行，因为在dosomethingBlock引用了ViewController，而Student又是ViewController属性，存在循环引用。 修改这个bug，只需要清掉其中一个引用即可
_stu = [[Student alloc]init];
[_stu startBlock:^(NSDictionary *dic) {
_dic = dic;
NSLog(@"%@",self.dic[@"key"]);
_stu = nil;
}];
[_stu callBackData];- 第二种
typedef void(^dosomethingBlock)(NSDictionary *dic);
@interface Student : NSObject
- (void)startBlock:(dosomethingBlock)block;
- (void)callBackData;
@end
#import "Student.h"
@interface Student()
@property (nonatomic,copy) dosomethingBlock block;
@end
@implementation Student
- (void)startBlock:(dosomethingBlock)block{
if (block) {
_block = block;
}
}
- (void)callBackData{
if (_block) {
_block(@{@"key":@"value"});
}
}
- (void)dealloc{
NSLog(@"%s",__func__);
}
@end
#import "ViewController.h"
#import "Student.h"
@interface ViewController ()
@property (nonatomic,strong) NSDictionary *dic;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
Student *_stu = [[Student alloc]init];
[_stu startBlock:^(NSDictionary *dic) {
_dic = dic;
NSLog(@"%@--%@",self.dic[@"key"],_stu);
}];
[_stu callBackData];
}
@end运行程序发现student的delloc不会执行，因为在dosomethingBlock引用了_stu自己，存在循环引用。 修改这个bug，只需要清掉其中一个引用即可
- (void)callBackData{
if (_block) {
_block(@{@"key":@"value"});
_block = nil;
}
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原始发表：2018-08-12，如有侵权请联系 cloudcommunity@tencent.com 删除
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