NSOperation的子集，简易方法的NSInvocationOperation －－（多线程）

多线程编程是防止主线程堵塞，增加运行效率等等的最佳方法。而原始的多线程方法存在很多的毛病，包括线程锁死等。在Cocoa中，Apple提供了NSOperation这个类，提供了一个优秀的多线程编程方法。



本次介绍NSOperation的子集，简易方法的NSInvocationOperation：

@implementation MyCustomClass

- (void)launchTaskWithData:(id)data

{

//创建一个NSInvocationOperation对象，并初始化到方法

//在这里，selector参数后的值是你想在另外一个线程中运行的方法（函数，Method）

//在这里，object后的值是想传递给前面方法的数据

NSInvocationOperation* theOp = [[NSInvocationOperation alloc] initWithTarget:self

selector:@selector(myTaskMethod:) object:data];

// 下面将我们建立的操作“Operation”加入到本地程序的共享队列中（加入后方法就会立刻被执行）

// 更多的时候是由我们自己建立“操作”队列

[[MyAppDelegate sharedOperationQueue] addOperation:theOp];

}

// 这个是真正运行在另外一个线程的“方法”

- (void)myTaskMethod:(id)data

{

// Perform the task.

}

@end一个NSOperationQueue 操作队列，就相当于一个线程管理器，而非一个线程。因为你可以设置这个线程管理器内可以并行运行的的线程数量等等。下面是建立并初始化一个操作队列：

@interface MyViewController : UIViewController {

NSOperationQueue *operationQueue;

//在头文件中声明该队列

}

@end

@implementation MyViewController

- (id)init

{

self = [super init];

if (self) {

operationQueue = [[NSOperationQueue alloc] init]; //初始化操作队列

[operationQueue setMaxConcurrentOperationCount:1];

//在这里限定了该队列只同时运行一个线程

//这个队列已经可以使用了

}

return self;

}

- (void)dealloc

{

[operationQueue release];

//正如Alan经常说的，我们是程序的好公民，需要释放内存！

[super dealloc];

}

@end简单介绍之后，其实可以发现这种方法是非常简单的。很多的时候我们使用多线程仅仅是为了防止主线程堵塞，而NSInvocationOperation就是最简单的多线程编程，在iPhone编程中是经常被用到的。

///////////////////////////////////////////////////////////////////////////////////////////////////

1 在主线程里加入一个loading画面……

2 {

3 [window addSubview:view_loading];

4 [NSThread detachNewThreadSelector:@selector(init_backup:) toTarget:self withObject:nil];

5 }

可以通过performSelectorOnMainThread更新UI元素，比如设置进度条等等。最后消除loading画面，载入主View。

7 - (void)init_backup:(id)sender

8 {

9 NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

10

11 // ...

12 int i = status;

13 [self performSelectorOnMainThread:@selector(show_loading:) withObject:[NSNumber numberWithInt:i] waitUntil Done:NO];

14

15 [view_loading removeFromSuperview];

16 [window addSubview:tabcontroller_main.view];

17 [pool release];

18 }

///////////////////////////////////////////////////////

利用iphone的多线程实现和线程同步

从接口的定义中可以知道，NSThread和大多数iphone的接口对象一样，有两种方式可以初始化：

一种使用initWithTarget:(id)target selector:(SEL)selector object:(id)argument，但需要负责在对象的retain count为0时调用对象的release方法清理对象。

另一种则使用所谓的convenient method,这个方便接口就是detachNewThreadSelector，这个方法可以直接生成一个线程并启动它，而且无需为线程的清理负责。

#import <UIKit/UIKit.h>

@interface SellTicketsAppDelegate : NSObject <UIApplicationDelegate> {

int tickets;

int count;

NSThread* ticketsThreadone;

NSThread* ticketsThreadtwo;

NSCondition* ticketsCondition;

UIWindow *window;

}

@property (nonatomic, retain) IBOutlet UIWindow *window;

@end

然后在实现中添加如下代码：

// SellTicketsAppDelegate.m

// SellTickets

//

//

#import "SellTicketsAppDelegate.h"

@implementation SellTicketsAppDelegate

@synthesize window;

- (void)applicationDidFinishLaunching:(UIApplication *)application {

tickets = 100;

count = 0;

// 锁对象

ticketCondition = [[NSCondition alloc] init];

ticketsThreadone = [[NSThread alloc] initWithTarget:self selector:@selector(run) object:nil];

[ticketsThreadone setName:@"Thread-1"];

[ticketsThreadone start];

ticketsThreadtwo = [[NSThread alloc] initWithTarget:self selector:@selector(run) object:nil];

[ticketsThreadtwo setName:@"Thread-2"];

[ticketsThreadtwo start];

//[NSThread detachNewThreadSelector:@selector(run) toTarget:self withObject:nil];

// Override point for customization after application launch

[window makeKeyAndVisible];

}

- (void)run{

while (TRUE) {

// 上锁

[ticketsCondition lock];

if(tickets > 0)

{

[NSThread sleepForTimeInterval:0.5];

count = 100 - tickets;

NSLog(@"当前票数是:%d,售出:%d,线程名:%@",tickets,count,[[NSThread currentThread] name]);

tickets--;

}else

{

break;

}

[ticketsCondition unlock];

}

}

- (void)dealloc {

[ticketsThreadone release];

[ticketsThreadtwo release];

[ticketsCondition release];

[window release];

[super dealloc];

}

@end

-------------------------------------------------------------------------------------

// 定义

#import <UIKit/UIKit.h>

@interface ThreadSyncSampleViewController : UIViewController {

int _threadCount;

NSCondition *_myCondition;

}

@end

//实现文件如下:

#import "ThreadSyncSampleViewController.h"

@implementation ThreadSyncSampleViewController

/*

// The designated initializer. Override to perform setup that is required before the view is loaded.

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {

if (self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]) {

// Custom initialization

}

return self;

}

*/

/*

// Implement loadView to create a view hierarchy programmatically, without using a nib.

- (void)loadView {

}

*/

// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.

- (void)viewDidLoad {

[super viewDidLoad];

//

//_myCondition = nil;

//

_myCondition = [[NSCondition alloc] init];

//

NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:30

target:self

selector:@selector(threadTester)

userInfo:nil

repeats:YES];

[timer fire];

}

- (void)threadTester{

[_myCondition lock];

_threadCount = -2;

//如果有n个要等待的thread，这里置成 -n

[_myCondition unlock];

//

NSLog(@"");

NSLog(@"------------------------------------------------------------------------------");

[NSThread detachNewThreadSelector:@selector(threadOne) toTarget:self withObject:nil];

[NSThread detachNewThreadSelector:@selector(threadTwo) toTarget:self withObject:nil];

[NSThread detachNewThreadSelector:@selector(threadThree) toTarget:self withObject:nil];

return;

}

- (void)threadOne{

NSLog(@"@@@ In thread 111111 start.");

[_myCondition lock];

int n = rand()%5 + 1;

NSLog(@"@@@ Thread 111111 Will sleep %d seconds ,now _threadCount is : %d",n,_threadCount);

sleep(n);

//[NSThread sleepForTimeInterval:n];

_threadCount ++ ;

NSLog(@"@@@ Thread 111111 has sleep %d seconds ,now _threadCount is : %d",n,_threadCount);

[_myCondition signal];

NSLog(@"@@@ Thread 1111111 has signaled ,now _threadCount is : %d",_threadCount);

[_myCondition unlock];

NSLog(@"@@@ In thread one complete.");

[NSThread exit];

return;

}

- (void)threadTwo{

NSLog(@"### In thread 2222222 start.");

[_myCondition lock];

int n = rand()%5 + 1;

NSLog(@"### Thread 2222222 Will sleep %d seconds ,now _threadCount is : %d",n,_threadCount);

sleep(n);

// [NSThread sleepForTimeInterval:n];

_threadCount ++ ;

NSLog(@"### Thread 2222222 has sleep %d seconds ,now _threadCount is : %d",n,_threadCount);

[_myCondition signal];

NSLog(@"### Thread 2222222 has signaled ,now _threadCount is : %d",_threadCount);

[_myCondition unlock];

//_threadCount ++ ;

NSLog(@"### In thread 2222222 complete.");

[NSThread exit];

return;

}

- (void)threadThree{

NSLog(@"<<< In thread 333333 start.");

[_myCondition lock];

while (_threadCount < 0) {

[_myCondition wait];

}

NSLog(@"<<< In thread 333333 ,_threadCount now is %d ,will start work.",_threadCount);

[_myCondition unlock];

NSLog(@"<<< In thread 333333 complete.");

[NSThread exit];

return;

}

/*

// Override to allow orientations other than the default portrait orientation.

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation {

// Return YES for supported orientations

return (interfaceOrientation == UIInterfaceOrientationPortrait);

}

*/

- (void)didReceiveMemoryWarning {

// Releases the view if it doesn't have a superview.

[super didReceiveMemoryWarning];

// Release any cached data, images, etc that aren't in use.

}

- (void)viewDidUnload {

// Release any retained subviews of the main view.

// e.g. self.myOutlet = nil;

}

- (void)dealloc {

[_myCondition release];

[super dealloc];

}

@end

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