Question

How do you compare the text in two text fields to see if they are the same, such as in “Password” and “Confirm Password” text fields?

if (passwordField == passwordConfirmField) {

    //they are equal to each other

} else {

    //they are not equal to each other

}

Answer 1

In Objective-C you should use isEqualToString:, like so:

if ([passwordField.text isEqualToString:passwordConfirmField.text]) {
    //they are equal to each other
} else {
    //they are *not* equal to each other
}

NSString is a pointer type. When you use == you are actually comparing two memory addresses, not two values. The text properties of your fields are 2 different objects, with different addresses.
So == will always¹ return false.

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In Swift things are a bit different. The Swift String type conforms to the Equatable protocol. Meaning it provides you with equality by implementing the operator ==. Making the following code safe to use:

let string1: String = "text"
let string2: String = "text"

if string1 == string2 {
    print("equal")
}

And what if string2 was declared as an NSString?

let string2: NSString = "text"

The use of == remains safe, thanks to some bridging done between String and NSString in Swift.

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1: Funnily, if two NSString object have the same value, the compiler may do some optimization under the hood and re-use the same object. So it is possible that == could return true in some cases. Obviously this not something you want to rely upon.