如何在objective-c ios中等待完成块完成
我有一个具有两种方法的子类:如何在objective-c ios中等待完成块完成,ios,objective-c,semaphore,completionhandler,completion-block,Ios,Objective C,Semaphore,Completionhandler,Completion Block,我有一个具有两种方法的子类: - (void) aPostRequest:(NSString *) urlStr andJSON:(NSMutableDictionary*) jsonDict completion:(void (^)(NSDictionary *, NSError *))completion { NSError *error = nil; NSURLSessionConfiguration *configuration = [NSURLSessionConfi
- (void) aPostRequest:(NSString *) urlStr andJSON:(NSMutableDictionary*) jsonDict completion:(void (^)(NSDictionary *, NSError *))completion
{
NSError *error = nil;
NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration];
NSURL *url = [NSURL URLWithString:urlStr];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];
[request setHTTPMethod:@"POST"];
[request addValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
[request addValue:@"application/json" forHTTPHeaderField:@"Accept"];
// Set up the post data
NSData *postData = [NSJSONSerialization dataWithJSONObject:jsonDict options:0 error:nil];
[request setHTTPBody:postData];
// dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
NSURLSessionDataTask *postDataTask = [session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error)
{
if (!error)
{
// convert the NSData response to a dictionary
NSDictionary *dictionary = [NSJSONSerialization JSONObjectWithData:data options:0 error:&error];
if (error)
{
// There is a parse error
completion(nil, error);
}
else
{
// Success
completion(dictionary, nil);
}
}
else
{
// Error from the session
completion(nil, error);
}
// dispatch_semaphore_signal(semaphore);
}];
// dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
[postDataTask resume];
}
此方法调用上述方法:
- (NSString *) verifyUnique
{
// JSON data
__block NSString *verifyUnique = nil;
// dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
// URL string
NSString *url = @"https://the-website-to-handle-this.com";
NSMutableDictionary *json = [[NSMutableDictionary alloc] init];
[json setValue:@"testing" forKey:@"name"];
[self aPostRequest:url andJSON:json completion:^(NSDictionary *response, NSError *error)
{
// dispatch_semaphore_signal(semaphore);
if (!error) {
} else {
verifyUnique = [response objectForKey:@"uniqueness"];
// return verifyUnique;
// dispatch_semaphore_signal(semaphore);
}
}];
// dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
return verifyUnique;
}
我从另一个视图控制器类调用该函数,并调用
[thisClass verifyUnique]
并希望它等待答案返回。在视图控制器中调用它之前,UI使用活动指示器进行处理,以便我们可以等待。如何等待两个完成块返回?您可以在verifyUnique
中添加完成块作为参数:
- (void)verifyUnique:(void (^)(NSString * str))handler{
// JSON data
__block NSString *verifyUnique = nil;
// dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
// URL string
NSString *url = @"https://the-website-to-handle-this.com";
NSMutableDictionary *json = [[NSMutableDictionary alloc] init];
[json setValue:@"testing" forKey:@"name"];
[self aPostRequest:url andJSON:json completion:^(NSDictionary *response, NSError *error)
{
// dispatch_semaphore_signal(semaphore);
if (!error) {
handler(@"");
} else {
verifyUnique = [response objectForKey:@"uniqueness"];
handler(verifyUnique);
}
}];
}
您可以这样使用它:
[object verifyUnique:^(NSString *verifyUnique) {
}];
使用以下命令:
[thisClass verifyUniqueCompletion:^(NSString *result, NSError) {
NSLog(@"result: ", result);
}];
这是一个快速的答案,我使用的是objective cYep,但是这里的想法,以及下面的两个答案,是您正在调用异步方法,所以您应该自己采用异步模式,并使用自己的完成处理程序模式,而不是等待响应。什么是异步模式?(我不知道swift,所以我很难读懂)另请看@cdub——异步模式只是一种用于解决特定问题的设计,在本例中是异步编程。最常见的异步模式之一是完成处理程序模式,即方法异步运行,但提供了完成处理程序参数,调用方可以通过该参数指定异步任务完成时应执行的代码。事实上,
dataTaskWithRequest
和aPostRequest
都采用了这种模式,我们都建议您自己的verifyUnique
也采用这种模式。请检查我编辑的答案。因此,如果我想在if语句中使用上面的结果,它必须位于该块的内部,对吗?比如如果(结果==@是
[thisClass verifyUniqueCompletion:^(NSString *result, NSError) {
NSLog(@"result: ", result);
}];