1. 用于数组: 表示长度与元素个数相同.golang
在golang中数组的长度是类型的一部分,不一样长度,不一样类型.c#
2. 用于参数: 用于形参表示可变参数. 用于实参表示直接传递. 具体解释参数见官方文档:数组
传递可变参数时:ui
(1) 若是实参后不跟..., 则在底层建立与形参类型相同的slice,而后将实参赋值后传递.this
(2) 若是实参后跟..., 则不在底层建立与形参类型相同的slice,而是直接将实参传递给形参.code
/ref/spec#Passing_arguments_to_..._parametersci
... parametersIf f is variadic with a final parameter p of type ...T, then within f the type of p is equivalent to type []T. If f is invoked with no actual arguments for p, the value passed to p is nil. Otherwise, the value passed is a new slice of type []T with a new underlying array whose successive elements are the actual arguments, which all must be assignable to T. The length and capacity of the slice is therefore the number of arguments bound to p and may differ for each call site.element
Given the function and calls文档
func Greeting(prefix string, who ...string)
Greeting("nobody")
Greeting("hello:", "Joe", "Anna", "Eileen")get
within Greeting, who will have the value nil in the first call, and []string{"Joe", "Anna", "Eileen"} in the second.
If the final argument is assignable to a slice type []T, it may be passed unchanged as the value for a ...T parameter if the argument is followed by .... In this case no new slice is created.
Given the slice s and call
s := []string{"James", "Jasmine"}Greeting("goodbye:", s...)
within Greeting, who will have the same value as s with the same underlying array.