In Swift 4.2 and Xcode 10.1
In Swift strings can be treated like an array of individual characters. So each character in string is like an element in array. To get the length of a string use yourStringName.count property.
In Swift
yourStringName.characters.count
property in deprecated. So directly use strLength.count
property.
let strLength = "This is my string"
print(strLength.count)
//print(strLength.characters.count) //Error: 'characters' is deprecated: Please use String or Substring directly
If Objective C
NSString *myString = @"Hello World";
NSLog(@"%lu", [myString length]); // 11