在 Swift 中使用三元运算符将 Double 转换为 String

Question

Need to eliminate extra zeros when working with doubles in swift eg (3.0 should output like 3 and 3.2 should be 3.2)

//description is String; operand is Double

// works
(operand - floor(operand) != 0) ? (description += String(operand)) : (description += String(Int(operand)))

// not works
description += String( (operand - floor(operand) != 0) ? operand : Int(operand) )

Why ternary operator is giving an error in second version? Is there any other way to avoid duplicate code?

Answer 1

There are a lot of rules regarding using the ternary operator. One of them is that the operand on the left and right side of the : character must be of compatible types.

In your code,

(operand - floor(operand) != 0) ? operand : Int(operand)

The left side of the : is a Double , while the right side is an Int . Double and Int are not compatible types, so it fails to compile.

A workaround for this:

description += "\((operand - floor(operand) != 0) ? operand as AnyObject: Int(operand) as AnyObject)"
// now the two sides are both AnyObjects now!

If you want even less duplicate code, in terms of number of characters, you can cast the two operands to Any instead of AnyObject .

Answer 2

description += String( (operand - floor(operand) != 0) ? operand : Int(operand) ). 

此三元运算具有不同的结果类型，double 和 int。