Changing the text of an existing UILabel can be done by accessing and modifying the text property of the UILabel. This can be done directly using String literals or indirectly using variables.
String literalsSwift
label.text = "the new text"
Objective-C
// Dot Notation
label.text = @"the new text";
// Message Pattern
[label setText:@"the new text"];
Swift
let stringVar = "basic String var"
label.text = stringVar
Objective-C
NSString * stringVar = @"basic String var";
// Dot Notation
label.text = stringVar;
// Message Pattern
[label setText: stringVar];