Swift: could not find an overload for '+' that accepts the supplied arguments

当两个变量或者常量 相加时 类型不一样 ，就会出此错 例如

var  stringOne = " swift "  

var numberOne = 94

错误：var stringNum = stringOne + numberOne

正确的做法: var stringNum = stringOne  + String(numberOne)

var  integerNum = 10

var  doubleNum = 10.0

错误： var addNum = integerNum + doubleNum

正确的做法: var addNum = Float(integerNum) + Float(doubleNum)