本篇文章主要介紹下多線程下NSOperation、NSBlockOperation、NSInvocationOperation、NSOperationQueue的使用，列舉幾個簡單的例子。
默認情況下，NSOperation并不具備封裝操作的能力，必須使用它的子類，使用NSOperation子類的方式有3種：
1> 自定義子類繼承NSOperation，實現內部相應的方法
2> NSBlockOperation
3>NSInvocationOperation
這講先介紹如何用NSOperation封裝一個操作，后面再結合NSOperationQueue來使用。
1.首先介紹自定義NSOperation：NSOperation是沒法直接使用的，它只是提供了一個工作的基本邏輯，具體實現還是需要你通過定義自己的NSOperation子類來獲得。
#import <Foundation/Foundation.h>
@protocol NSDefineOprationDelegate <NSObject>
- (void) handleDelegate;
@end
@interface NSDefineOpration : NSOperation
@property (nonatomic, assign) id <NSDefineOprationDelegate> delegate;
- (id)initWithDelegate:(id<NSDefineOprationDelegate>) delegate;
@end
實現文件里：
#import "NSDefineOpration.h"
@implementation NSDefineOpration
- (id)initWithDelegate:(id<NSDefineOprationDelegate>) delegate
{
if(self = [super init])
{
self.delegate = delegate;
}
return self;
}
- (void)main
{
@autoreleasepool {
//do something
sleep(15);
NSLog(@"op1........handle...... on thread num :%@",[NSThread currentThread]);
if([self.delegate respondsToSelector:@selector(handleDelegate)])
{
[self.delegate performSelector:@selector(handleDelegate) withObject:nil];
}
}
}
@end
這里的sleep（15）主要用來做一些延時的操作，比如網絡下載等。調用：
- (void)oprationTest
{
NSDefineOpration *op1 = [[NSDefineOpration alloc] initWithDelegate:self];
op1.completionBlock = ^(){
NSLog(@"op1........OK !!");
};
[op1 start];
}
執行結果：
2017-07-25 12:07:01.051 No.22 Foundation_NSOperation[20340:1394940] op1........handle...... on thread num :<NSThread: 0x600000067c80>{number = 1, name = main}
2017-07-25 12:07:01.052 No.22 Foundation_NSOperation[20340:1395366] op1........OK !!
從執行結果可以看出，因為在實現的main函數里沒有使用異步線程處理，導致直接阻塞了主線程1，所以使用這種方式一定注意main函數里操作時間過長導致主線程阻塞問題。耗時比較長的都放到其他線程里處理。
2.接下來介紹NSBlockOperation
第一種使用NSBlockOperation的方式：
NSLog(@"block start");
NSBlockOperation *bop2 = [NSBlockOperation blockOperationWithBlock:^{
sleep(15);
NSLog(@"bop2.....handle..... on thread num%@",[NSThread currentThread]);
}];
[bop2 setCompletionBlock:^{
NSLog(@"bop2........OK !!");
}];
[bop2 start];
- 第2行初始化了一個NSBlockOperation對象，它是用一個Block來封裝需要執行的操作
- 第9行調用了start方法，緊接著會馬上執行Block中的內容
看下執行結果：
2017-07-25 13:48:15.948 No.22 Foundation_NSOperation[20717:1441242] block start
2017-07-25 13:48:30.950 No.22 Foundation_NSOperation[20717:1441242] bop2.....handle..... on thread num<NSThread: 0x608000062780>{number = 1, name = main}
2017-07-25 13:48:30.951 No.22 Foundation_NSOperation[20717:1441598] bop2........OK !!
- 這里還是在當前線程同步執行操作，并沒有異步執行，阻塞主線程。
第二種使用NSBlockOperation的方式：
- (void)blockOprationTest
{
NSLog(@"block start");
NSBlockOperation * op2 = [[NSBlockOperation alloc] init];
[op2 addExecutionBlock:^{
sleep(10);
NSLog(@"op2.....handle..... on 10 hread num%@",[NSThread currentThread]);
}];
[op2 addExecutionBlock:^{
sleep(6);
NSLog(@"op2.....handle..... on 6 thread num%@",[NSThread currentThread]);
}];
[op2 addExecutionBlock:^{
sleep(4);
NSLog(@"op2.....handle..... on 4 thread num%@",[NSThread currentThread]);
}];
[op2 addExecutionBlock:^{
sleep(8);
NSLog(@"op2.....handle..... on 8 thread num%@",[NSThread currentThread]);
}];
[op2 addExecutionBlock:^{
sleep(1);
NSLog(@"op2.....handle..... on 1 thread num%@",[NSThread currentThread]);
}];
[op2 setCompletionBlock:^{
NSLog(@"op2........OK !!");
}];
[op2 start];
//bop2
NSBlockOperation *bop2 = [NSBlockOperation blockOperationWithBlock:^{
sleep(15);
NSLog(@"bop2.....handle..... on thread num%@",[NSThread currentThread]);
}];
[bop2 setCompletionBlock:^{
NSLog(@"bop2........OK !!");
}];
[bop2 start];
}
執行結果：
2017-07-25 13:49:35.830 No.22 Foundation_NSOperation[20740:1443207] block start
2017-07-25 13:49:39.899 No.22 Foundation_NSOperation[20740:1443307] op2.....handle..... on 4 thread num<NSThread: 0x60800026a780>{number = 4, name = (null)}
2017-07-25 13:49:40.971 No.22 Foundation_NSOperation[20740:1443307] op2.....handle..... on 1 thread num<NSThread: 0x60800026a780>{number = 4, name = (null)}
2017-07-25 13:49:41.900 No.22 Foundation_NSOperation[20740:1443254] op2.....handle..... on 6 thread num<NSThread: 0x608000261dc0>{number = 3, name = (null)}
2017-07-25 13:49:43.902 No.22 Foundation_NSOperation[20740:1443255] op2.....handle..... on 8 thread num<NSThread: 0x60000007df80>{number = 5, name = (null)}
2017-07-25 13:49:45.832 No.22 Foundation_NSOperation[20740:1443207] op2.....handle..... on 10 hread num<NSThread: 0x60800006e780>{number = 1, name = main}
2017-07-25 13:49:45.832 No.22 Foundation_NSOperation[20740:1443255] op2........OK !!
2017-07-25 13:50:00.833 No.22 Foundation_NSOperation[20740:1443207] bop2.....handle..... on thread num<NSThread: 0x60800006e780>{number = 1, name = main}
2017-07-25 13:50:00.834 No.22 Foundation_NSOperation[20740:1443564] bop2........OK !!
分析下結果：
首先看到了有1和2兩個線程，線程2在56秒的時候開始執行6秒的操作，接下來執行4，1秒結束時間為07秒。線程1在56的時候開始執行10秒的操作，接下來執行8秒，結束時間為14秒。最后執行Bop2的15秒操作至29秒。時間看起來沒有問題。為什么會啟用2個線程而不是3個或者更多？
3.接下來介紹NSInvocationOperation
- (void)invocationOperation
{
NSInvocationOperation * op3 = [[NSInvocationOperation alloc] initWithTarget:(id)self selector:@selector(handleInvoOpD) object:nil];
[op3 setCompletionBlock:^{
NSLog(@"op3........OK !!");
}];
[op3 start];
}
selector函數：
- (void)handleInvoOpD
{
sleep(5);
NSLog(@"op3.....handle..... on thread num :%@",[NSThread currentThread]);
}
執行結果：
2017-07-25 13:52:19.661 No.22 Foundation_NSOperation[20766:1446216] op3.....handle..... on thread num :<NSThread: 0x6000000662c0>{number = 1, name = main}
2017-07-25 13:52:19.662 No.22 Foundation_NSOperation[20766:1446254] op3........OK !!
NSInvocationOperation比較簡單，就是繼承了NSOperation，區別就是它是基于一個對象和selector來創建操作，可以直接使用而不需繼承來實現自己的操作處理。
4.最后介紹下NSOperationQueue
把NSOperation子類的對象放入NSOperationQueue隊列中，該隊列就會啟動并開始處理它。隊列里可以加入很多個NSOperation, 可以把NSOperationQueue看作一個線程池，可往線程池中添加操作（NSOperation）到隊列中。線程池中的線程可看作消費者，從隊列中取走操作，并執行它。
實現demo：
- (void)handleOpqueue
{
NSOperationQueue *qu = [[NSOperationQueue alloc] init];
NSBlockOperation * bkOp1 = [NSBlockOperation blockOperationWithBlock:^{
sleep(10);
NSLog(@"bkOp1.....handle.....on thread num%@",[NSThread currentThread]);
}];
[bkOp1 setCompletionBlock:^{
NSLog(@"bkOp1........OK !!");
}];
NSBlockOperation * bkOp2 = [NSBlockOperation blockOperationWithBlock:^{
sleep(2);
NSLog(@"bkOp2.....handle.....on thread num%@",[NSThread currentThread]);
}];
[bkOp2 setCompletionBlock:^{
NSLog(@"bkOp2........OK !!");
}];
NSBlockOperation * bkOp3 = [NSBlockOperation blockOperationWithBlock:^{
sleep(1);
NSLog(@"bkOp3.....handle.....on thread num%@",[NSThread currentThread]);
}];
[bkOp3 setCompletionBlock:^{
NSLog(@"bkOp3........OK !!");
}];
NSBlockOperation * bkOp4 = [NSBlockOperation blockOperationWithBlock:^{
sleep(10);
NSLog(@"bkOp4.....handle.....on thread num%@",[NSThread currentThread]);
}];
[bkOp4 setCompletionBlock:^{
NSLog(@"bkOp4........OK !!");
}];
NSBlockOperation * bkOp5 = [NSBlockOperation blockOperationWithBlock:^{
sleep(5);
NSLog(@"bkOp5.....handle.....on thread num%@",[NSThread currentThread]);
}];
[bkOp5 setQueuePriority:NSOperationQueuePriorityHigh];
[bkOp5 setCompletionBlock:^{
NSLog(@"bkOp5........OK !!");
}];
NSInvocationOperation *invoOp6 = [[NSInvocationOperation alloc] initWithTarget:(id)self selector:@selector(handleInvoOp) object:nil];
[invoOp6 setCompletionBlock:^{
NSLog(@"invoOp6........OK !!");
}];
[invoOp6 setQueuePriority:NSOperationQueuePriorityHigh];
[qu setMaxConcurrentOperationCount:2];
[qu addOperation:bkOp3];
[qu addOperation:bkOp2];
[qu addOperation:bkOp1];
[qu addOperation:bkOp4];
[qu addOperation:bkOp5];
[qu addOperation:invoOp6];
}
先看下執行結果：
2017-07-25 13:53:59.235 No.22 Foundation_NSOperation[20790:1448570] bkOp3.....handle.....on thread num<NSThread: 0x600000266780>{number = 3, name = (null)}
2017-07-25 13:53:59.236 No.22 Foundation_NSOperation[20790:1448675] bkOp3........OK !!
2017-07-25 13:54:00.201 No.22 Foundation_NSOperation[20790:1448573] bkOp2.....handle.....on thread num<NSThread: 0x60800026ed80>{number = 4, name = (null)}
2017-07-25 13:54:00.202 No.22 Foundation_NSOperation[20790:1448573] bkOp2........OK !!
2017-07-25 13:54:04.311 No.22 Foundation_NSOperation[20790:1448569] bkOp5.....handle.....on thread num<NSThread: 0x6000002733c0>{number = 5, name = (null)}
2017-07-25 13:54:04.311 No.22 Foundation_NSOperation[20790:1448573] bkOp5........OK !!
2017-07-25 13:54:05.276 No.22 Foundation_NSOperation[20790:1448570] op3.....handle..... on thread num :<NSThread: 0x600000266780>{number = 3, name = (null)}
2017-07-25 13:54:05.277 No.22 Foundation_NSOperation[20790:1448573] invoOp6........OK !!
2017-07-25 13:54:14.385 No.22 Foundation_NSOperation[20790:1448569] bkOp1.....handle.....on thread num<NSThread: 0x6000002733c0>{number = 5, name = (null)}
2017-07-25 13:54:14.386 No.22 Foundation_NSOperation[20790:1448573] bkOp1........OK !!
2017-07-25 13:54:15.349 No.22 Foundation_NSOperation[20790:1448570] bkOp4.....handle.....on thread num<NSThread: 0x600000266780>{number = 3, name = (null)}
2017-07-25 13:54:15.350 No.22 Foundation_NSOperation[20790:1448573] bkOp4........OK !!
從結果可以看出，NSOperationQueue在2，3，4這3個線程里去處理NSOperation，而不包括主線程1。此外，在設置了bkop5以及invOp6的優先級為高時，他們會優先執行，當然這個優先時相對，是相對正在排隊的，不包括已經正在執行的。
總結：NSOperation、NSBlockOperation、NSInvocationOperation、NSOperationQueue都比較簡單，NSOperation、NSBlockOperation、NSInvocationOperation單個都是表示一種操作，而NSOperationQueue是一個可以包含多個NSOperation的隊列，可以自己在多個線程處理，只要加入隊列之后，我們就不用去操作，直到Callback或者完成。
