How can I truncate an NSString to a set length?

Swift 4

let trimToCharacter = 20
let shortString = String(myString.prefix(trimToCharacter))

Happy Coding.

Actually the part about being "Unicode safe" was dead on, as many characters combine in unicode which the suggested answers don't consider.

For example, if you want to type é. One way of doing it is by typing "e"(0x65)+combining accent" ́"(0x301). Now, if you type "café" like this and truncate 4 chars, you'll get "cafe". This might cause problems in some places.

If you don't care about this, other answers work fine. Otherwise, do this:

// define the range you're interested in
NSRange stringRange = {0, MIN([myString length], 20)};

// adjust the range to include dependent chars
stringRange = [myString rangeOfComposedCharacterSequencesForRange:stringRange];

// Now you can create the short string
NSString *shortString = [myString substringWithRange:stringRange];

Note that in this way your range might be longer than your initial range length. In the café example above, your range will expand to a length of 5, even though you still have 4 "glyphs". If you absolutely need to have a length less than what you indicated, you need to check for this.