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NSConditionLockはどのように使用しますか？またはNSCondition

ある関数を別の関数で待機させようとしています。これを実現するためにNSCondionLockを使用したいと思います。私は助けを求めていませんが、誰かが私にNSConditionLockを説明するためのまともなチュートリアルまたは例を示してくれること、またはおそらくより良い方法を提案できることを本当に望んでいます。

iphoneioslockingconditional-statements
31
gurooj

編集： @Bonshingtonがコメントしたように、この回答はNSConditionを指します（NSConditionLockではなく）：

- (void) method1 {

    [myCondition lock];
    while (!someCheckIsTrue)
        [myCondition wait];


    // Do something.


    [myCondition unlock];
}

- (void) method2 {

    [myCondition lock];


    // Do something.


    someCheckIsTrue = YES;
    [myCondition signal];
    [myCondition unlock];
}

someCheckIsTrueは何でもかまいません。単純なBOOL変数でも、[myArray count] == 0 && color == kColorRedのようなものでもかまいません。それは重要ではありません。ある方法では、ロックをチェックしながらロックを確認し、別の方法では、条件をtrueにすることができる変更を加えますロックをかけている間も。魔法はwaitとsignalの部分です。waitは実際にロックを解除し、signalと呼ばれる他のスレッドの後でロックを再取得します。

49
DarkDust

ここでサンプルテストクラスが必要な人のために、私が試してみたことを投稿し、NSConditionがどのように機能するかを理解します。

// --- MyTestClass.h File --- //
@interface MyTestClass

- (void)startTest;

@end

// --- MyTestClass.m File --- //
@implementation MyTestClass
{
    NSCondition *_myCondition;
    BOOL _someCheckIsTrue;
}

- (id)init
{
    self = [super init];
    if (self) 
    {
        _someCheckIsTrue = NO;
        _myCondition = [[NSCondition alloc] init];
    }
    return self;
}

#pragma mark Public Methods

- (void)startTest
{
    [self performSelectorInBackground:@selector(_method1) withObject:nil];

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        sleep(5);
        [self performSelectorInBackground:@selector(_method2) withObject:nil];
    });
}

#pragma mark Private Methods

- (void)_method1
{
    NSLog(@"STARTING METHOD 1");

    NSLog(@"WILL LOCK METHOD 1");
    [_myCondition lock];
    NSLog(@"DID LOCK METHOD 1");

    while (!_someCheckIsTrue)
    {
        NSLog(@"WILL WAIT METHOD 1");
        [_myCondition wait];
        NSLog(@"DID WAIT METHOD 1");
    }

    NSLog(@"WILL UNLOCK METHOD 1");
    [_myCondition unlock];
    NSLog(@"DID UNLOCK METHOD 1");

    NSLog(@"ENDING METHOD 1");
}

- (void)_method2
{
    NSLog(@"STARTING METHOD 2");

    NSLog(@"WILL LOCK METHOD 2");
    [_myCondition lock];
    NSLog(@"DID LOCK METHOD 2");

    _someCheckIsTrue = YES;

    NSLog(@"WILL SIGNAL METHOD 2");
    [_myCondition signal];
    NSLog(@"DID SIGNAL METHOD 2");

    NSLog(@"WILL UNLOCK METHOD 2");
    [_myCondition unlock];
    NSLog(@"DID UNLOCK METHOD 2");
}

@end


// --- Output --- //
/*
2012-11-14 11:01:21.416 MyApp[8375:3907] STARTING METHOD 1
2012-11-14 11:01:21.418 MyApp[8375:3907] WILL LOCK METHOD 1
2012-11-14 11:01:21.419 MyApp[8375:3907] DID LOCK METHOD 1
2012-11-14 11:01:21.421 MyApp[8375:3907] WILL WAIT METHOD 1
2012-11-14 11:01:26.418 MyApp[8375:4807] STARTING METHOD 2
2012-11-14 11:01:26.419 MyApp[8375:4807] WILL LOCK METHOD 2
2012-11-14 11:01:26.419 MyApp[8375:4807] DID LOCK METHOD 2
2012-11-14 11:01:26.420 MyApp[8375:4807] WILL SIGNAL METHOD 2
2012-11-14 11:01:26.420 MyApp[8375:4807] DID SIGNAL METHOD 2
2012-11-14 11:01:26.421 MyApp[8375:4807] WILL UNLOCK METHOD 2
2012-11-14 11:01:26.421 MyApp[8375:3907] DID WAIT METHOD 1
2012-11-14 11:01:26.421 MyApp[8375:4807] DID UNLOCK METHOD 2
2012-11-14 11:01:26.422 MyApp[8375:3907] WILL UNLOCK METHOD 1
2012-11-14 11:01:26.423 MyApp[8375:3907] DID UNLOCK METHOD 1
2012-11-14 11:01:26.423 MyApp[8375:3907] ENDING METHOD 1
*/
32
vilanovi

NSConditionLockサンプルプログラム。

#import <Foundation/Foundation.h>

#define IDLE 0
#define START 1
#define TASK_1_FINISHED 2
#define TASK_2_FINISHED 3
#define CLEANUP_FINISHED 4

#define SHARED_DATA_LENGTH 1024 * 1024 * 1024

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        NSConditionLock *lock = [[NSConditionLock alloc] initWithCondition:IDLE];
        char *shared_data = calloc(SHARED_DATA_LENGTH, sizeof(char));

        [NSThread detachNewThreadWithBlock:^{
            [lock lockWhenCondition:START];

            NSLog(@"[Thread-1]: Task 1 started...");
            for (size_t i = 0; i < SHARED_DATA_LENGTH; i++) {
                shared_data[i] = 0x00;
            }
            [lock unlockWithCondition:TASK_1_FINISHED];
        }];

        [NSThread detachNewThreadWithBlock:^{
            [lock lockWhenCondition:TASK_1_FINISHED];
            NSLog(@"[Thread-2]: Task 2 started...");
            for (size_t i = 0; i < SHARED_DATA_LENGTH; i++) {
                char c = shared_data[i];
                shared_data[i] = ~c;
            }
            [lock unlockWithCondition:TASK_2_FINISHED];
        }];

        [NSThread detachNewThreadWithBlock:^{
            [lock lockWhenCondition:TASK_2_FINISHED];

            NSLog(@"[Thread-3]: Cleaning up...");
            free(shared_data);
            [lock unlockWithCondition:CLEANUP_FINISHED];
        }];

        NSLog(@"[Thread-main]: Threads set up. Waiting for 2 task to finish");
        [lock unlockWithCondition:START];
        [lock lockWhenCondition:CLEANUP_FINISHED];
        NSLog(@"[Thread-main]: Completed");
    }
    return 0;
}
3
GRiMe2D

Swift 5 Playgroundからの@ GRiMe2D回答のバージョン：

let myCondition = NSCondition()

var someCheckIsTrue = false

func method1() {
    print("STARTING METHOD 1")

    print("WILL LOCK METHOD 1")
    myCondition.lock()
    print("DID LOCK METHOD 1")

    while (!someCheckIsTrue) {
        print("WILL WAIT METHOD 1")
        myCondition.wait()
        print("DID WAIT METHOD 1")
    }

    print("WILL UNLOCK METHOD 1")
    myCondition.unlock()
    print("DID UNLOCK METHOD 1")

    print("ENDING METHOD 1")
}

func method2() {
    print("STARTING METHOD 2")

    print("WILL LOCK METHOD 2")
    myCondition.lock()
    print("DID LOCK METHOD 2")

    someCheckIsTrue = true

    print("WILL SIGNAL METHOD 2")
    myCondition.signal()
    print("DID SIGNAL METHOD 2")

    print("WILL UNLOCK METHOD 2")
    myCondition.unlock()
    print("DID UNLOCK METHOD 2")

    print("ENDING METHOD 2")
}

DispatchQueue.global().async {
    method1()
}

DispatchQueue.global().asyncAfter(deadline: DispatchTime.now() + 0.5) {
    method2()
}
0
Ivan Smetanin