btn.frame = CGRectMake(i*(320/tabArray.count), 0, 320/tabArray.count, 49);

但是到了swift裡這麼來寫是行不通的，編譯不通過，找了下寫法如下

var button:UIButton = UIButton()
            var z = (idx)*135
            var c = CGFloat(z)
            var x:CGFloat = 107.0 + c
            var frame = CGRectMake(x, 20, 135, 53)
            button.frame = frame
 

OC寫法：

[NSString stringWithFormat:@"%.2ld",(long)row];

swift中的寫法：

NSString(format: "tabbar_unselected%d",idx)