iOS 多线程的使用（Operation）

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];

   不能直接Operation是因为它里面没有直接操作的方法 只是一个基类 （抽象类）

    NSInvocationOperation *invocation0 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(act:) object:@"invocation0"];

    如果单独使用Operation 必须手动启动

    [invocation start];

  Operation是在当前线程去执行（同步执行）

    NSInvocationOperation *invocation1 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(act:) object:@"invocation1"];

    NSInvocationOperation *invocation2 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(act:) object:@"invocation2"];

    NSInvocationOperation *invocation3 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(act:) object:@"invocation3"];

    NSInvocationOperation *invocation4 = [[NSInvocationOperation alloc]initWithTarget:self selector:@selector(act:) object:@"invocation4"];

    

    NSBlockOperation *blockOperation = [NSBlockOperation blockOperationWithBlock:^{

       具体执行的方法  任务

        [self act:@"blockOperation"];

    }];

    

       添加操作

    NSBlockOperation 的操作数大于1 的时候  会开辟线程去执行

    [blockOperation addExecutionBlock:^{

        [self act:@"blockOperation2"];

    }];

    [blockOperation start];

   operation 默认在当期线程去执行 （同步执行）

    

可以使用线程队列NSOperationQueue去管理线程 (默认会开辟线程去执行)  异步执行 不用手动去启动线程

    NSOperationQueue *queue = [[NSOperationQueue alloc]init];

可以线程队列的最大并发数（最多允许多少操作同时执行）

    queue.maxConcurrentOperationCount = 3;

   设置Operation的依赖关系

    [invocation1 addDependency:invocation0];

    [invocation2 addDependency:invocation1];

    [invocation3 addDependency:invocation2];

    [invocation4 addDependency:invocation3];

    [blockOperation addDependency:invocation4];

    

    [queue addOperation:invocation0];

    [queue addOperation:invocation1];

    [queue addOperation:invocation2];

    [queue addOperation:invocation3];

    [queue addOperation:invocation4];

    [queue addOperation:blockOperation];

}

- (void)act:(id)sender

{

    NSLog(@"%@%@",[NSThread currentThread],sender);

}

@end