提示：队列的取出是有顺序的，与打印结果并不矛盾。这就好比，选手A,BC虽然起跑的顺序是先A,后B，然后C，但是到达终点的顺序却不一定是A,B在前，C在后。
下面使用for循环打印，可以更明显的看出任务是并发执行的。
代码示例：
复制代码#import "YYViewController.h"
@interface YYViewController ()
@end
复制代码
@implementation YYViewController
- (void)viewDidLoad
{
[super viewDidLoad];
//创建NSInvocationOperation对象，封装操作
NSInvocationOperation *operation1=[[NSInvocationOperation alloc]initWithTarget:self selector:@selector(test1) object:nil];
NSInvocationOperation *operation2=[[NSInvocationOperation alloc]initWithTarget:self selector:@selector(test2) object:nil];
//创建对象，封装操作
NSBlockOperation *operation3=[NSBlockOperation blockOperationWithBlock:^{
for (int i=0; i<5; i++) {
NSLog(@"NSBlockOperation3--1----%@",[NSThread currentThread]);
}
}];
[operation3 addExecutionBlock:^{
for (int i=0; i<5; i++) {
NSLog(@"NSBlockOperation3--2----%@",[NSThread currentThread]);
}
}];
//创建NSOperationQueue
NSOperationQueue * queue=[[NSOperationQueue alloc]init];
//把操作添加到队列中
[queue addOperation:operation1];
[queue addOperation:operation2];
[queue addOperation:operation3];
}
-(void)test1
{
for (int i=0; i<5; i++) {
NSLog(@"NSInvocationOperation--test1--%@",[NSThread currentThread]);
}
}
-(void)test2
{
for (int i=0; i<5; i++) {
