Swift NSString function syntax usage

Question

I have a basic question about swift function calling syntax. I have read documentation but not able to figure it out. So decided to put a query over here.

A piece of code i wrote

    var string1 = NSString().stringByAppendingString("First string")
    var string2 = NSString.stringByAppendingString("Second string")

    println(string1)
    println(string2)

Both string have same function calling but return type is different. And only difference here is (). I got out put like

First string

(Function)

Question is why its not giving a warning/error. Is it that var string2 holds method body of stringByAppendingString? Whats going on, New swift developer like me can easily make a this type of typo mistake and not able to figure out.

Can you please explain why its not return value?

Vladimir · Accepted Answer · 2014-11-14 11:25:54Z

6

This happens because swift methods are curried functions (you can find detailed explanation in Ole Begemann's post).

So what you actually got in the following line:

var string2 = NSString.stringByAppendingString("Second string")

is a function that takes a string as parameter and returns the result of

"Second string".stringByAppendingString(parameter)

You can check that by calling string2 as an ordinary function:

string2("123")
// Prints: "Second string123"

answered Nov 14, 2014 at 11:25

Vladimir

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