dispatch_group_t 的使用

多个任务并发执行， 完成后在做某个事情

#import "GroupObject.h"
@interface GroupObject() {
//    并发队列
    dispatch_queue_t concurrent_queue;
}
//    容器

@property (nonatomic, strong) NSMutableArray *muArray;
@end

@implementation GroupObject
 - (instancetype)init {
    if (self = [super init]) {
        //创建一个并发队列
        concurrent_queue = dispatch_queue_create("mutliread_group", DISPATCH_QUEUE_CONCURRENT);
    }
    return self;
}

- (void)handleGroup {
    dispatch_group_t group = dispatch_group_create();
    for (NSString *str in _muArray) {
        dispatch_group_async(group, concurrent_queue, ^{
            NSLog(@"str");
        });
    }
    
    dispatch_group_notify(group, concurrent_queue, ^{
        NSLog(@"end");
    });
}
@end