我的应用程序中有以下方法，它使用String[] elements = xml.split("<");
LinkedList<String> ll = new LinkedList<String>();
for (String str : elements) {
if (str.isEmpty())
continue;
str = str.trim();
if (ll.isEmpty()) {
ll.add(str);
continue;
}
if (!ll.peekLast().equals(str)) {
ll.add(str);
}
}
while (!ll.isEmpty()) {
System.out.println("<" + ll.pollFirst());
}
从JSON格式的Web服务中提取电影数据：
NSURLSession上面的代码工作正常。没有问题。但是，我现在要做的是重构我的代码，以便在包含我的- (void) downloadMovieData {
//this is just a visual cue to show that processing is being done
[[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];
//creating the request
NSURL *url = [NSURL URLWithString:kMovieURL];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
//creating the session
self.config = [NSURLSessionConfiguration defaultSessionConfiguration];
self.session = [NSURLSession sessionWithConfiguration:self.config];
//the object that makes the call to the web service using the request and the session, and returns a response or an error
NSURLSessionDataTask *task = [self.session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
//At this point a response has been received, so we can turn the indicator off
[[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];
//I am casting the response to an NSHTTPURLResponse so I can check the status code of the response
NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;
//a status code of 200 means a successful connection with the web service
if (httpResponse.statusCode == 200) {
dispatch_async(dispatch_get_main_queue(), ^{
NSLog(@"Success!");
//I send the data that was received from the response to the method so that the JSON data is extracted
[self populateArray:data];
});
} else {
NSString *result = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSLog(@"Received HTTP %ld: %@", (long)httpResponse.statusCode, result);
}
}];
[task resume];
}
- (void) populateArray: (NSData *)data {
NSError *jsonError;
NSDictionary *response =[NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:&jsonError];
if (response) {
self.movieObjects = response[@"movies"];
NSLog(@"The movie objects are: %@", self.movieObjects);
[self.tableView reloadData];
} else {
NSLog(@"ERROR: %@", jsonError);
}
}
委托方法的类中包含所有网络代码，我想将代码移动到使用Singleton的单独类中更好地分离代码的方法。我有以下框架代码，如下所示：
UITableView我完全理解Singleton类没有问题。这不是问题。我的问题是理解如何理解＆＃34;完成处理程序＆＃34;这个方法的一部分：
#import "Networker.h"
@implementation Networker
+ (NSURLSession *)dataSession {
static NSURLSession *session = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration]];
});
return session;
}
+ (void)fetchContentsOfURL:(NSURL *)url completion:(void (^)(NSData *data, NSError *error)) completionHandler {
NSURLSessionDataTask *dataTask = [[self dataSession] dataTaskWithURL:url
completionHandler: ^(NSData *data, NSURLResponse *response, NSError *error) {
if (completionHandler == nil) return;
if (error) {
completionHandler(nil, error);
return;
}
completionHandler(data, nil);
}];
[dataTask resume];
}
我想做的是将我在方法中的代码移动到＆＃34; downloadMovieData＆＃34;，进入＆＃34; fetchContentsOfURL＆＃34;，并返回一个+ (void)fetchContentsOfURL:(NSURL *)url completion:(void (^)(NSData *data, NSError *error)) completionHandler {}
对象然后我可以使用在我的调用类中填充UITableView。但是，在这样做的过程中，我想确保我理解＆＃34; completionHandler＆＃34;这种新方法的一部分。我怎么能这样做？
答案 0 :(得分：1)
你不能移动它所以它返回，因为它是异步的。从技术上讲，你可以，但是在你等待的时候你会阻塞主线程。
相反，您只需用对单例的调用替换当前代码，在完成块中调用其他方法来处理数据。
需要注意的事项：