__NSCFNumber stringByAddingPercentEncodingWithAllowedCharacters unrecognized selector error - ios

Question

So Im new in programming with Objective-c. I want to make request with HTTP POST Method.The parameter that i'm sending is of type int.
I'm getting this error :
[__NSCFNumber stringByAddingPercentEncodingWithAllowedCharacters:]: unrecognized selector sent to instance 0xb0000000000048d3
at this line of code :
return [string stringByAddingPercentEncodingWithAllowedCharacters:allowed];
The whole Code:
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
[request setValue:#"application/x-www-form-urlencoded" forHTTPHeaderField:#"Content-Type"];
request.HTTPMethod = #"POST";
[request setHTTPBody:[self httpBodyForParameters:params]];
NSURLSessionTask *task = [[NSURLSession sharedSession] dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
if (error) {
NSLog(#"dataTaskWithRequest error: %#", error);
}
if ([response isKindOfClass:[NSHTTPURLResponse class]]) {
NSInteger statusCode = [(NSHTTPURLResponse *)response statusCode];
if (statusCode != 200) {
NSLog(#"Expected responseCode == 200; received %ld", (long)statusCode);
}}
NSError *parseError;
id responseObject = [NSJSONSerialization JSONObjectWithData:data options:0 error:&parseError];
if (!responseObject) {
NSLog(#"JSON parse error: %#", parseError);
} else {
NSLog(#"responseObject = %#", responseObject);
}
NSLog(#"print123");
}];
[task resume];
}
- (NSData *)httpBodyForParameters:(NSDictionary *)parameters {
NSMutableArray *parameterArray = [NSMutableArray array];
[parameters enumerateKeysAndObjectsUsingBlock:^(NSString *key, NSString *obj, BOOL *stop) {
NSString *param = [NSString stringWithFormat:#"%#=%#", [self percentEscapeString:key], [self percentEscapeString:obj]];
[parameterArray addObject:param];
}];
NSString *string = [parameterArray componentsJoinedByString:#"&"];
return [string dataUsingEncoding:NSUTF8StringEncoding];
}
- (NSString *)percentEscapeString:(NSString *)string {
NSCharacterSet *allowed = [NSCharacterSet characterSetWithCharactersInString:#"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-._~"];
return [string stringByAddingPercentEncodingWithAllowedCharacters:allowed];
}

Answer 1

#Paulw11 is right that the error is the result of a number being treated as a string. An immediate (but a little clunky) fix is to be less committed to the type of values you find when enumerating the dictionary...
// notice we change the type of obj id, not NSString*
[parameters enumerateKeysAndObjectsUsingBlock:^(NSString *key, id obj, BOOL *stop) {
// now, test for it's type and treat accordingly
NSString *objString = ([obj isKindOfClass:[NSString self]])? [self percentEscapeString:obj] : [obj stringValue];
NSString *param = [NSString stringWithFormat:#"%#=%#", [self percentEscapeString:key], objString];
[parameterArray addObject:param];
}];
But this brittle solution now works only for strings and numbers. If you can convince the server to accept JSON, then the request code can be simplified and generalized like this...
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
[request setValue:#"application/x-www-form-urlencoded" forHTTPHeaderField:#"Content-Type"];
request.HTTPMethod = #"POST";
// params is your original (serializable) dictionary
NSError *error;
NSData *postData = [NSJSONSerialization dataWithJSONObject: params options:0 error:&error];
[request setHTTPBody:postData];
NSURLSessionTask *task = // ...