[英]IOS, Swift, No way to access main thread in NSURLSession
我正在使用Swift创建一个iOS应用。 我想实现一些GET或POST HTTP请求。 我知道Alamofire存在,但我想创建自己的函数。
我做了什么 :
import Foundation
class DatabaseRequest:NSObject{
class func GET(urlAsString:String, completion : (response:NSURLResponse, result:AnyObject?, error:String?)-> Void){
let configuration = NSURLSessionConfiguration.ephemeralSessionConfiguration()
let session = NSURLSession(configuration: configuration)
let url = NSURL(string: urlAsString)
let urlRequest = NSMutableURLRequest(URL: url!)
urlRequest.HTTPMethod = "GET"
session.dataTaskWithRequest(urlRequest, completionHandler: { (data, response, error) -> Void in
if let error = error{
dispatch_async(dispatch_get_main_queue(), { () -> Void in
completion(response: response, result: nil, error: "GET Connection error : \(error.localizedDescription)")
})
}else{
var error:NSError?
let JSON_Object:AnyObject? = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.AllowFragments, error: &error)
if let error = error{
dispatch_async(dispatch_get_main_queue(), { () -> Void in
completion(response: response, result: nil, error: "GET JSONSerialization error: \(error.localizedDescription)")
})
}else{
if let result:AnyObject = JSON_Object{
//The third time I use this class function, no way to access the main thred to send data
dispatch_async(dispatch_get_main_queue(), { () -> Void in
completion(response: response, result: JSON_Object, error: nil)
})
}else{
dispatch_async(dispatch_get_main_queue(), { () -> Void in
completion(response: response, result: nil, error: nil)
})
}
}
}
session.finishTasksAndInvalidate()
}).resume()
}
class func POST(urlAsString:String, parameters:[String:AnyObject], completion:(response:NSURLResponse?, result:AnyObject?, error:String?)->Void){
println("POST used")
let configuration = NSURLSessionConfiguration.ephemeralSessionConfiguration()
let session = NSURLSession(configuration: configuration)
var errorHTTPBody:NSError?
let url = NSURL(string: urlAsString)
let urlRequest = NSMutableURLRequest(URL: url!)
urlRequest.addValue("application/json", forHTTPHeaderField: "Content-Type")
urlRequest.addValue("application/json", forHTTPHeaderField: "Accept")
urlRequest.HTTPMethod = "POST"
urlRequest.HTTPBody = NSJSONSerialization.dataWithJSONObject(parameters, options: nil, error: &errorHTTPBody)
if let error = errorHTTPBody{
dispatch_async(dispatch_get_main_queue(), { () -> Void in
completion(response: nil, result: nil, error: "POST errorHTTPBody: \(error.localizedDescription)")
})
return
}
session.dataTaskWithRequest(urlRequest, completionHandler: { (data, response, error) -> Void in
println(data)
if let error = error{
dispatch_async(dispatch_get_main_queue(), { () -> Void in
completion(response: response, result: nil, error: "POST Connection error : \(error.localizedDescription)")
})
}else{
var error:NSError?
var JSON_Object:AnyObject? = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.AllowFragments, error: &error)
if let error = error{
dispatch_async(dispatch_get_main_queue(), { () -> Void in
completion(response: response, result: nil, error: "POST JSONSerialization error : \(error.localizedDescription)")
})
}else{
if let result:AnyObject = JSON_Object{
dispatch_async(dispatch_get_main_queue(), { () -> Void in
completion(response: response, result: JSON_Object, error: nil)
})
}else{
dispatch_async(dispatch_get_main_queue(), { () -> Void in
completion(response: response, result: nil, error: nil)
})
}
}
}
session.finishTasksAndInvalidate()
}).resume()
}
}
有趣的部分主要是GET函数(因为POST函数的作用相同)。 好吧,一切似乎都正常。 我实现了两次使用此GET函数,但是第三次使用它,无法访问主线程来发送数据。 我可以在评论之前//The third time I use this class function, no way to access the main thread to send data
之前记录一些内容//The third time I use this class function, no way to access the main thread to send data
但是没有任何日志记录在dispatch_async(dispatch_get_main_queue(),block)
。
任何想法?
您在这里尝试的操作对我来说有点奇怪。 您正在从主线程异步调度到主线程。 通常,您分派异步操作以在当前线程以外的另一个线程上并行执行某项操作,因此当前线程可以继续执行其操作,而不必等待异步任务的完成。 当我与主线程无关时,调度到同一线程会使任务排队等待稍后执行。 我不明白为什么要在主线程上执行这些任务。 只要您不尝试操作UI对象,任何线程都可以。 我真的只会在触摸UI时使用主线程。 现在开始执行HTTP提取或发布的问题,我建议遵循Apple传播的方法。 那就是使用委托来处理异步回调。 苹果已经定义了三种委托协议:NSURLSessionDelegate,NSURLSessionTaskDelegate,NSURLSessionDataDelegate。 我将创建一个类,例如实现以下协议的HTTPClient:
@interface HTTPClient : NSObject <NSURLSessionDelegate, NSURLSessionTaskDelegate, NSURLSessionDataDelegate>
@property (strong, nonatomic) NSURLSession *session;
@property (strong, nonatomic) NSMutableDictionary *runningTasks;
- (void) URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data;
- (void) URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error;
- (NSURLSessionTask *) startGetTaskForURL: (NSURL *) url;
@end
@implementation HTTPClient
- (NSURLSessionTask *) startGetTaskForURL: (NSURL *) url {
NSURLSessionTask *task = [self.session dataTaskWithURL:url];
NSMutableData *data = [NSMutableData data];
[task resume];
[self.runningTasks setObject:data forKey:task];
return task;
}
- (void) URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *) dataTask didReceiveData: (NSData *)data {
NSString *dataString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSMutableData *runningData = [self.runningTasks objectForKey:task];
if (!runningData) {
NSLog(@"No data found for task");
}
[runningData appendData: data];
}
- (void) URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error {
NSData *data = [self.runningTasks objectForKey:task];
//process the data received
}
@end
收到所有数据后,您可以执行必要的JSON处理。 当然,您需要初始化字典runningTasks。
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