How to get the type of a function in Golang?

In Golang, we can use the reflect.TypeOf() function to get the function type: get the function type: fnType := reflect.TypeOf(add) print the function type: fmt.Println("function type: ", fnType) get Function name: fmt.Println("Function name: ", fnType.Name()) Get function parameter type: for i := 0; i < fnType.NumIn(); i { fmt.Println("- ", fnType .In(i)) }Get the function return value type: for i := 0; i < fnType.NumOut(); i { fmt.Println("- ", fnType.Out(i)) }

How to get the type of function in Golang?

In Golang, we can use the reflect.TypeOf() function to get the type of any variable or expression, including functions. This function returns a reflect.Type object that provides information about the type, including name, underlying type, methods, and fields.

The following is a code example of how to use reflect.TypeOf() to obtain the function type:

package main

import (
    "fmt"
    "reflect"
)

func add(a, b int) int {
    return a + b
}

func main() {
    // 获取 add 函数的类型
    fnType := reflect.TypeOf(add)

    // 打印函数类型
    fmt.Println("函数类型：", fnType)

    // 获取函数名称
    fmt.Println("函数名称：", fnType.Name())

    // 获取函数参数类型
    numInParams := fnType.NumIn()
    fmt.Println("参数类型：")
    for i := 0; i < numInParams; i++ {
        paramType := fnType.In(i)
        fmt.Println("-", paramType)
    }

    // 获取函数返回值类型
    numOutParams := fnType.NumOut()
    fmt.Println("返回值类型：")
    for i := 0; i < numOutParams; i++ {
        resultType := fnType.Out(i)
        fmt.Println("-", resultType)
    }
}

Practical case:

We can use this technique to build advanced functions that support different function types. For example, we can write a function to execute any reflection-based function:

package main

import (
    "fmt"
    "reflect"
)

func callFunction(fn interface{}, args ...interface{}) interface{} {
    fnType := reflect.TypeOf(fn)
    numInParams := fnType.NumIn()

    // 检查调用函数的参数与函数签名是否匹配
    if len(args) != numInParams {
        panic("参数数量与函数签名不匹配")
    }

    // 设置函数调用参数的 reflection 值
    fnArgs := make([]reflect.Value, len(args))
    for i := 0; i < len(args); i++ {
        fnArgs[i] = reflect.ValueOf(args[i])
    }

    // 执行函数调用
    result := reflect.ValueOf(fn).Call(fnArgs)

    // 获取并返回函数调用的结果
    resultValue := result[0].Interface()
    return resultValue
}

func main() {
    // 使用带有整型参数的 add 函数
    addResult := callFunction(add, 5, 10)
    fmt.Println("add(5, 10) =", addResult)

    // 使用带有字符串参数的 concat 함수
    concatResult := callFunction(func(s1, s2 string) string { return s1 + s2 }, "Hello", "World!")
    fmt.Println("concat(\"Hello\", \"World!\") =", concatResult)
}

By using reflect.TypeOf() to get the function type, we can build powerful and flexible programs.

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