我正在创建一个启用了 ARC 的 iPhone 应用程序,在这种情况下我遇到了这种情况。
在应用程序的每个页面中,都会发生 Web 服务调用。在这种方法中,我在从服务器添加新值之前从数组中删除所有对象。一切正常,但有时应用程序在[self.myArray removeAllObjects]
.
我为 myArray 设置了@property@property (strong, nonatomic) NSMutableArray myArray;
我在想的是,当我使用 ARC 时,对象 ,myArray
在某个时候被释放,我尝试从同一个数组中删除所有对象。这导致崩溃,我不确定,但我没有看到任何其他原因。
因此,我正在考虑在删除其中的对象之前检查数组是否有效。我写了一个示例代码来检查不同的场景。这里是:
NSMutableArray *testArray = [[NSMutableArray alloc]initWithObjects:@"1", @"2", @"3", @"4", nil];
if (testArray) {
NSLog(@"i am alive");
}
[testArray release];
if (testArray) { //here how to check whether this array is valid or not?
NSLog(@"i am alive: %@", testArray);
}else{
NSLog(@"I am dead");
testArray = [[NSMutableArray alloc]initWithObjects:@"5", @"6", @"7", @"8", nil];
}
[testArray release];
[testArray removeAllObjects];
我知道这会导致崩溃,但这只是为了检查。在这里,如何检查数组是否有效?这是一个正确的方法还是别的什么?
请指导我。
谢谢。
实际代码:
- (void)getFriendsList{
BOOL netIsAvailable = [self connected];
if (netIsAvailable) {
@try {
NSString *accessToken = [self getAccessToken];
NSString *tokenEncoded = [accessToken stringByReplacingOccurrencesOfString:@"\"" withString:@""];
NSString *finalUrl = [NSString stringWithFormat:@"%@FriendsnSongs/%@",CommonWebServiceUrl,tokenEncoded];
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:finalUrl] cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:10];
NSURLResponse *response = nil;
NSError *error = nil;
NSData *currentResult = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
// NSString* responseString = [[NSString alloc] initWithData:currentResult encoding:NSUTF8StringEncoding];
if (currentResult != nil) {
NSDictionary* json = [NSJSONSerialization
JSONObjectWithData:currentResult
options:kNilOptions
error:&error];
NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;
int statusCode = [httpResponse statusCode];
NSMutableArray *match = [json valueForKey:@"FriendsnSongsResult"];
if (statusCode == 200) {
if (self.userGuidArray) {
[self.albumNameArray removeAllObjects]; //here got crash
[self.artistNameArray removeAllObjects];
[self.deviceNameArray removeAllObjects]; //here also got crash once
[self.nickNameArray removeAllObjects];
[self.userProfileImageArray removeAllObjects];
[self.songTitleArray removeAllObjects];
[self.songStatusArray removeAllObjects];
[self.userGuidArray removeAllObjects];
}
for(NSArray *player in match) {
[self.albumNameArray addObject:[(NSArray *)player valueForKey:@"AlbumName"]];
[self.artistNameArray addObject:[(NSArray *)player valueForKey:@"Artist"]];
[self.nickNameArray addObject:[(NSArray *)player valueForKey:@"NickName"]];
[self.userProfileImageArray addObject:[(NSArray *)player valueForKey:@"ProfileImage"]];
[self.songStatusArray addObject:[(NSArray *)player valueForKey:@"Status"]];
[self.songTitleArray addObject:[(NSArray *)player valueForKey:@"Title"]];
[self.userGuidArray addObject:[(NSArray *)player valueForKey:@"UserGuid"]];
[self.deviceNameArray addObject:[(NSArray *)player valueForKey:@"DeviceName"]];
}
//Start timer for updating the friends list
if (timerActivated)
[self performSelectorOnMainThread:@selector(backgroundFriendsListUpdate) withObject:nil waitUntilDone:NO];
//Update table if the table not in search mode
if (!isSearching)
[self performSelectorOnMainThread:@selector(updateTable) withObject:nil waitUntilDone:YES];
}
}
}
@catch (NSException *exception) {
NSLog(@"Exception: %@",exception.name);
}
}
[DejalActivityView removeView];
}
重要的一点是,在这个类中,每 30 秒运行一个后台线程。它将调用相同的方法来刷新表。