go-variable Parameters

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

Today, when trying to write a simple ORM with go, I find that when you call a variadic function, you don't always use the ellipsis to expand a slice, and sometimes the compiler may make an error by using a few simple examples as a description.

We usually use an empty interface when we're unsure of the data type.

tests1(789)fmt.Println("-------------")tests1("789")

func tests1(arg interface{}) {    fmt.Println("value:", arg)    fmt.Println("type:", reflect.TypeOf(arg).Name())}

Output results

value: 789type: int-------------value: 789type: string

When using variable entry parameters of the same type

tests([]string{"4", "5", "6"}...)

func tests(args ...string) {    for i, v := range args {        fmt.Println(i, "----", v)    }}

Output results

0 ---- 41 ---- 52 ---- 6

When using interface{} as a variable entry parameter

func testParams(args ...interface{}) {    for i, v := range args {        if s, ok := v.(string); ok {            fmt.Println("----", s)        }        if s, ok := v.([]string); ok {            for i, v := range s {                fmt.Println(i, "[]----", v)            }        }        fmt.Println(i, v)    }}

Error occurred

cannot use []string literal (type []string) as type []interface {} in argument to testParams      

When we see this, the answer is already on the surface.
Two solutions available here

The first of these methods

s := []string{"4", "5", "6"}var d []interface{} = []interface{}{s[0], s[1], s[2]}testParams(d...)

Results

---- 40 4---- 51 5---- 62 6

The second method of

s := []string{"4", "5", "6"}var d []interface{}d = append(d, s)testParams(d...)

Results

0 []---- 41 []---- 52 []---- 60 [4 5 6]

Summary: The arguments passed in when using interface{} as a variable input parameter do type conversions