我正在从自定义 NSObject 类获取 Twitter 时间线数据,并且此类具有调用 API 和解析数据的所有 coe。 我从我的 View Controller 调用此类,它有一个 TableView ,需要用来自 Twitter 的数据填充 TableView 。但是由于 dispatch_sync 的一些问题,我的 View Controller 调用了 twitter 类,并且在数组(我用来填充 TableView )填充数据之前控制权返回到 View Controller 。
这是一些代码:
#import <UIKit/UIKit.h>
#import "SecondViewController.h"
#import "SpinnerController.h"
#import "proAlertView.h"
#import "SBJson.h"
#import <Accounts/Accounts.h>
#import <Twitter/Twitter.h>
@interface TwitterDataLoad : NSObject<UIAlertViewDelegate>
{
NSMutableData * receivedData;
NSArray * results;
NSArray * cellContent;
NSMutableArray * totalContent;
SpinnerController * spinner;
proAlertView * av;
NSString *json_string;
NSDictionary * jsonResults;
SBJsonParser * parser;
NSMutableArray * dataForTable;
}
@property(nonatomic, strong) ACAccount * account;
@property(nonatomic, strong) NSArray * accounts;
@property(nonatomic, strong) ACAccountStore * accountStore;
@property (nonatomic ,retain) SecondViewController * tbView;
- (void)loadData;
@end
#import "TwitterDataLoad.h"
@interface TwitterDataLoad ()
@end
@implementation TwitterDataLoad
@synthesize tbView;
-(id) init {
self = [super init];
if (self) {
[self loadData];
}
return self;
}
- (void)loadData
{
dataForTable = [[NSMutableArray alloc]init];
//Twitter new code
if (_accounts == nil) {
if (_accountStore == nil) {
_accountStore = [[ACAccountStore alloc] init];
}
ACAccountType *accountTypeTwitter =
[_accountStore
accountTypeWithAccountTypeIdentifier:ACAccountTypeIdentifierTwitter];
[_accountStore requestAccessToAccountsWithType:accountTypeTwitter
withCompletionHandler:^(BOOL granted, NSError *error) {
if(granted) {
dispatch_sync(dispatch_get_main_queue(), ^{
_accounts = [_accountStore
accountsWithAccountType:accountTypeTwitter];
[self sendRequest];
});
}
}];
}
}
-(void) sendRequest {
totalContent = [[NSMutableArray alloc]init];
_account = [_accounts objectAtIndex:0];
TWRequest *postRequest = [[TWRequest alloc]
initWithURL:
[NSURL URLWithString:@"https://api.twitter.com/1/statuses/user_timeline.json?screen_name=test&count=20"]
parameters:nil
requestMethod:TWRequestMethodGET];
av = [[proAlertView alloc]initWithTitle:nil message:@"Getting latest news..." delegate:self cancelButtonTitle:nil otherButtonTitles:nil, nil];
UIActivityIndicatorView * indicator = [[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
indicator.frame = CGRectMake(120, 55, 35, 35);
[av addSubview:indicator];
[indicator startAnimating];
[av setBackgroundColor:[UIColor clearColor] withStrokeColor:[UIColor blackColor]];
[av show];
[postRequest setAccount:_account];
[postRequest performRequestWithHandler:^(NSData *responseData,
NSHTTPURLResponse *urlResponse,
NSError *error) {
if ([urlResponse statusCode] == 200) {
NSError *jsonError = nil;
results = [NSJSONSerialization JSONObjectWithData:responseData options:0 error:&jsonError];
dispatch_sync(dispatch_get_main_queue(), ^{
[av dismissAlert];
[self parseJson];
});
}
else {
[self showMessage];
}
}];
}
-(void)showMessage {
av = [[proAlertView alloc]initWithTitle:@"Connection Problem" message:@"Please confirm the device is connected to the Internet." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
[av setBackgroundColor:[UIColor clearColor] withStrokeColor:[UIColor blackColor]];
[av show];
}
-(void)parseJson {
NSMutableArray * complete = [[NSMutableArray alloc]init];
for (NSDictionary * tweets in results)
{
NSString * status = [tweets objectForKey:@"text"];
NSString * date = [tweets objectForKey:@"created_at"];
NSDictionary * user = [tweets objectForKey:@"user"];
NSString * artistName = [user objectForKey:@"name"];
NSString * screenName = [user objectForKey:@"screen_name"];
NSString * artistImage = [user objectForKey:@"profile_image_url"];
cellContent = [NSArray arrayWithObjects:status,date,artistName,screenName,artistImage, nil];
[complete addObject:cellContent];
}
SecondViewController * tmpView = [[SecondViewController alloc]initWithNibName:@"SecondViewController_iPhone" bundle:nil];
tmpView.dataToDisplay = complete;
}
这个类是这样调用的:
- (void)viewDidLoad
{
[super viewDidLoad];
TwitterDataLoad * data = [[TwitterDataLoad alloc] init];
[data loadData];
NSArray * temp = dataToDisplay;
}
我知道我以错误的方式返回值,但我尝试通过 loadData 消息本身将其返回到 View Controller ,但它也不起作用,所以我只是尝试这样做。请不要关心这个。
谢谢
最佳答案
好吧,我发现了这个问题。 dispatch_sync 正在做它应该做的事情,问题在于调用 dispatch_sync 的其他两个语句(其他 block )
[_accountStore requestAccessToAccountsWithType:accountTypeTwitter
withCompletionHandler:^(BOOL granted, NSError *error)
所以这是一个异步调用,当程序控制回到主队列时调用 dispatch sync,因为我们这样定义它:dispatch_sync(dispatch_get_main_queue()) 并且该方法在控件返回到主队列之前返回,因此数组没有获得任何值。 所以为了解决这个问题,我在我的调用类中写了一个 block ,一旦这个数据调用结束,它就会得到返回调用。如果你想要整个代码@ghostsmitm@gmail.com给我发邮件
关于ios - 如何正确使用dispatch_sync?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/13224344/