[英]iOS: Unrecognized selector sent to instance
I have a class where I request information from a provider class, in which after finalizing the job (asynchronous httpRequest block) needs to invoke a method [- (void) updateCountries] in the requester class. 我有一个我从提供程序类中请求信息的类,在该类中,完成作业(异步httpRequest块)后,需要在请求者类中调用方法[-(void)updateCountries]。 If I am not wrong this code worked in iOS 7, but now in iOS 8 it does not.
如果我没有记错的话,此代码可在iOS 7中使用,但现在在iOS 8中则无效。
Can you please help me to understand why? 你能帮我理解为什么吗?
Methods in requester class: 请求者类中的方法:
- (void) viewWillAppear:(BOOL)animated {
//get countries to pickerView
webAPI = [[WebAPI alloc] init];
[webAPI retrieveCountries:self];
}
- (void) updateCountries {
//update countries content for pickerView
locationDAO = [[LocationDAO alloc] init];
countriesArray = [locationDAO getCountries];
[pickerView reloadAllComponents];
}
Lines in method in provider class where error happens: 提供程序类中方法中发生错误的行:
SEL updateCountries = sel_registerName("updateCountries:");
[requester performSelectorOnMainThread:updateCountries withObject:nil waitUntilDone:YES];
If you need to checkout the entire method in the provider class, here it is: 如果您需要在提供程序类中检出整个方法,则为:
- (void) retrieveCountries:(id)requester {
// NSLog(@"engine report: firing retrieveCountries http get");
NSString *urlAsString = kRetrieveCountriesListAPI;
NSURL *url = [NSURL URLWithString:urlAsString];
NSMutableURLRequest *urlRequest = [NSMutableURLRequest requestWithURL:url];
[urlRequest setTimeoutInterval:30.0f];
[urlRequest setHTTPMethod:@"GET"];
[urlRequest setValue:@"application/json" forHTTPHeaderField:@"Content-type"];
[NSURLConnection sendAsynchronousRequest:urlRequest queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
if ([data length] >0 && error == nil){
NSString *response = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSLog(@"engine report: retrieveCountries server response: %@", response);
NSArray *level0 = [[NSArray alloc] initWithObjects:[NSJSONSerialization JSONObjectWithData:[[NSData alloc] initWithData:data] options:kNilOptions error:&error], nil];
NSArray *level1 = [level0 objectAtIndex:0];
LocationDAO *locationDAO = [[LocationDAO alloc] init];
[locationDAO deleteAllFromCountries];
for (int i = 0; i < [level1 count]; i++) {
CountryVO *countryVO = [[CountryVO alloc] init];
countryVO.myID = [[[level1 objectAtIndex:i] objectForKey:@"id"] integerValue];
countryVO.name = [[level1 objectAtIndex:i] objectForKey:@"country_name"];
[locationDAO saveCountryToDatabase:countryVO];
}
SEL updateCountries = sel_registerName("updateCountries:");
[requester performSelectorOnMainThread:updateCountries withObject:nil waitUntilDone:YES];
dispatch_async(dispatch_get_main_queue(), ^(void){
});
} else if ([data length] == 0 && error == nil){
NSLog(@"Nothing was downloaded.");
} else if (error != nil) {
NSLog(@"Error happened = %@", error);
} }];
}
THANK YOU A WHOLE LOT 谢谢你
Remove the :
from the selector specification: 卸下
:
从选择规范:
SEL updateCountries = sel_registerName("updateCountries");
Your method updateCountries
doesn't take any arguments. 您的方法
updateCountries
不接受任何参数。 So, when creating the selector , you should only write updateCountries
(instead of updateCountries:
which would indicate that this method takes an argument). 因此,在创建选择器时 ,您只应编写
updateCountries
(而不是updateCountries:
这表明该方法接受一个参数)。
The reason why your app crashes is that when you try to perform this selector, the internals of your app are looking for a method called updateCountries
on requester
that takes one argument. 您的应用程序崩溃的原因是,当您尝试执行此选择器时,您的应用程序内部会在
requester
程序上寻找一种名为updateCountries
的方法,该方法接受一个参数。 This method doesn't exist, which is why the app crashes. 此方法不存在,这就是应用程序崩溃的原因。
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