Application of semaphore and @synchronized of signal volume

1.//Create Global queue

dispatch_queue_t queue = dispatch_get_global_queue(0, 0);

Create semaphore

dispatch_semaphore_t semaphore = dispatch_semaphore_create(1);

nsmutablearray *array = [nsmutablearray array];

for(int i = 0 ; i < 1000000; i + +) {

dispatch_async(queue, ^{

Dispatch_semaphore Semaphore is a multi-threaded synchronization mechanism based on counter. When multiple threads access a common resource, there is a problem of data error caused by the feature of multithreading, which causes it to wait for the previous thread to access the array

dispatch_semaphore_wait(semaphore, dispatch_time_forever);

[array addobject: [nsnumber numberwithint: i]];

});

}

2.

dispatch_queue_t queue = dispatch_get_global_queue(0, 0);

nsmutablearray *array = [nsmutablearray array];

for(int i = 0 ; i < 1000000; i + +) {

dispatch_async(queue, ^{

Adds a lock to the array object. Prevents thread access at the same time.

@synchronized (array) {

[Array addobject: [nsnumber numberwithint: i]];

NSLog(@ "%d%@", I,array);

            }      

});

}

Application of semaphore and @synchronized of signal volume