文字と数字の変換

数字文字列　→　数字

Objective-C

    NSString *str = @"100";

    int a = [str intValue];

Swift

    let str = "100"

    let a:Int = str.toInt()!

数字　→　文字列

Objective-C

    int a = 100;

    NSString *str = [NSString stringWithFormat:@"%d",a];

Swift

    let a = 100

    let str1 = "\(a)"

    let str2 = a.description

str1の方はObjective-CのstringWithFormat的な書き方。

str2の方がSwift的で楽だね。