1 . 對于變量: 格式化數(shù)字字面量
通過使用下劃線可以提高數(shù)字字面量的可讀性
let testNumA = 123_456
let testNumB = 123.45_67
let testNumC = 123.000_456
print(testNumA)
print(testNumB)
print(testNumC)
打印結(jié)果
123456
123.4567
123.000456
2 . 對于元組: 忽略元組的元素值
當我們使用元組時胖笛，如果有的元素不需要使用燕垃，這時可以使用下劃線將相應的元素進行忽略
let http404Error = (404, "Not Found")
let (_, errorMessage) = http404Error
print(http404Error)
print(errorMessage)
打印結(jié)果
(404, "Not Found")
Not Found
3 . 對于數(shù)組: 忽略區(qū)間值
有時候我們并不關(guān)心區(qū)間內(nèi)每一項的值，可以使用下劃線來忽略這些值术健。
var base = 1;
let arr = [1,2,3,4,5,6,7,8,9,10]
print(arr)
for _ in 1...arr.count {
base += base
}
print(base)
打印結(jié)果
1024
4 . 對于函數(shù): 忽略外部參數(shù)名
- (1)忽略方法的默認外部參數(shù)名
- (2)忽略具有默認值的參數(shù)的外部參數(shù)名
func RGBA_1( r:CGFloat, g:CGFloat, b:CGFloat, a:CGFloat) -> UIColor {
return UIColor(red: (r)/255.0, green: (g)/255.0, blue: (b)/255.0, alpha: a)
}
func RGBA_2(_ r:CGFloat, g:CGFloat, b:CGFloat, a:CGFloat) -> UIColor {
return UIColor(red: (r)/255.0, green: (g)/255.0, blue: (b)/255.0, alpha: a)
}
func RGBA_3(_ r:CGFloat,_ g:CGFloat, b:CGFloat, a:CGFloat) -> UIColor {
return UIColor(red: (r)/255.0, green: (g)/255.0, blue: (b)/255.0, alpha: a)
}
func RGBA_4(_ r:CGFloat,_ g:CGFloat,_ b:CGFloat, a:CGFloat) -> UIColor {
return UIColor(red: (r)/255.0, green: (g)/255.0, blue: (b)/255.0, alpha: a)
}
func RGBA_5(_ r:CGFloat,_ g:CGFloat,_ b:CGFloat, _ a:CGFloat) -> UIColor {
return UIColor(red: (r)/255.0, green: (g)/255.0, blue: (b)/255.0, alpha: a)
}
func RGBA_6(_ r:CGFloat,_ g:CGFloat,_ b:CGFloat, _ a:CGFloat = 255) -> UIColor {
return UIColor(red: (r)/255.0, green: (g)/255.0, blue: (b)/255.0, alpha: a)
}
函數(shù)
方法調(diào)用
調(diào)用
PS :
不過為了提高代碼的可讀性，一般不進行忽略
