如何在Objective -C XCode中比较两个String

Question

I am checking user credential from WebAPI userId and userPWD and checking them. If User is valid then he access the app. If not then I am showing AlertView Controller to user that he is not valid user. How to do that. Please give me the example.

I post my code here:

if([jstr isEqualToString:@"Invalide Login Credential."])
{
    UIAlertController *alert=
          [UIAlertController alertControllerWithTitle:@"Enter valid Details." message:@"invalid" preferredStyle:UIAlertControllerStyleAlert];

    UIAlertAction* ok = 
          [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction * action)
    {                                                                         
       [alert dismissViewControllerAnimated:YES completion:nil];                                                                         
    }];
   [alert addAction:ok];

   [self presentViewController:alert animated:YES completion:nil];

   NSLog(@"Invalide Login Credential.");


   //Invalide Login Credential.

}

Response for its here :

Jstr = Invalide Login Credential.

Answer 1

if([jstr isEqualToString:@"Invalide Login Credential."])
{
    //Invalide Login Credential. with UIAlertController
}
else
{
    //valid user, do whatever you want the conditions here
}

Answer 2

Try this :

 if ([jstr rangeOfString:@"Invalide Login Credential." options:NSCaseInsensitiveSearch].location == NSNotFound) {
      // show error alertViewControler
 }
 else {
    NSLog(@"matched");
}

Answer 3

== compares the address of the objects, not their content. Two different objects will obviously never have the same address. To compare strings use NSString's isEqualToString: method:

if ([string1 isEqualToString:string2]) {
NSLog(@"it is equal");

}

Note the square brackets [ ]. This is the proper Objective-C syntax for sending messages (ie calling functions).