token 异步

子线程同时发起多个异步操作，需要得到上一个操作的回调，再执行下一个操作。
所有操作暂时全部放入数组，通过对数组操作，使队列每次只放一个操作任务，依次执行完毕。直到数组为空，所有操作都完成。这么做，可解决token短时间过期，经常更换，app同时发起多个请求被强制下线的问题。

//
//  ViewController.m
//  lockDemo
//
//  Created by huant on 2018/12/3.
//  Copyright © 2018年 huant. All rights reserved.
//

#import "ViewController.h"

@interface ViewController ()

@property (nonatomic, strong) NSMutableArray * opens;

@property (nonatomic, strong) NSOperationQueue * queue;

@end

@implementation ViewController

static int a = 1000;

- (void)viewDidLoad {
    [super viewDidLoad];

    self.opens = [[NSMutableArray alloc] init];
   
    NSBlockOperation * block = [NSBlockOperation blockOperationWithBlock:^{
        
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(5 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
            NSLog(@"================");
            [self removeOp];
        });
        for (int i = 0; i<100; i++) {
            [self print:@"111"];
            
        }
        
        
    }];
    
    NSBlockOperation * block1 = [NSBlockOperation blockOperationWithBlock:^{
        for (int i = 0; i<100; i++) {
            [self print:@"222222222"];
            
        }
        [self removeOp];

    }];
    
    NSBlockOperation * block2 = [NSBlockOperation blockOperationWithBlock:^{
        for (int i = 0; i<100; i++) {
            [self print:@"33333333333333"];
            
        }
        [self removeOp];

    }];

    [self.opens addObject:block];
    [self.opens addObject:block1];
    [self.opens addObject:block2];
    
    [self.queue addOperation:self.opens.firstObject];

}

- (void)removeOp{
    if (_opens.count) {
        [self.opens removeObjectAtIndex:0];

    }
    if (self.opens.count) {
        [self.queue addOperation:self.opens.firstObject];

    }
   
}

- (NSOperationQueue *)queue{
    if (!_queue) {
        _queue = [NSOperationQueue new];
    }
    return _queue;
}

- (void)print:(NSString *)str{
    @synchronized (self) {
        NSLog(@"%@", str);
//        NSLog(@"%@", [NSThread currentThread]);
        --a;
        NSLog(@"%d", a);
    }
}

@end