Golang variable Parameters

This is a creation in Article, where the information may have evolved or changed.

The day before yesterday colleague mentioned an example, about the use of variable parameters in Golang, usually do not pay attention to this detail, first on the code bar.

Test code

The code logic you want to implement is clear.

1. Testargs accepts an int parameter, an indefinite length argument, and a type of interface{}

2. Nums as slice, use ... After the grammatical sugar is beaten, afferent Testargs

It looks like logic's fine, do the error.

# command-line-arguments

./test.go:13:cannot use Nums (Type []int64) as type []interface {} ' argument to Testargs

Unexpectedly the type does not match, write Go also a year, this piece of cognition is too not in place, always think will nums, and then to interface{} This common type composition interface{} slice to Testargs.

So, let's see what happens when the nums goes in:

Slice

After executing the output []interface {}, the confirmation is to pass the variable parameter as slice to the function, which is similar to Python. Let's see if slice is the same one.

Fetch Address

After execution the output is as follows

Main addr of Slice 0xc82000c0c0

Testargs addr of Slice 0xc82000c0c0

The same address, if the variable parameter passed in itself is by slice ... form, then use the slice directly, and you will not create a new slice. So I understand the variable-parameter execution of Go:

for func (first int, arg ... T

1. When the variable parameter is not passed, the corresponding Arg is nil

2. When passing a single mutable parameter, actually executes [] T{ARG1,ARG2,ARG3}

3. Incoming ... The slice of the grammatical sugars, use this slice directly

This is why we understand why the small example of the opening is not executed, []int64 and []interface{} are two types of slice.