Can Go Pass Functions as Parameters Like Java?

Functions as Parameters in Go

In programming languages like Java, it is possible to pass functions as parameters to other functions. This allows for a high degree of flexibility and code reuse. Does Go offer a similar capability?

Go's Function Closure

Yes, Go supports the passing of functions as parameters through a concept known as function closures. Closures are functions that can refer to and retain the scope and variables of the enclosing function from which they are declared.

Implementation

In Go, functions are first-class citizens, meaning they can be assigned to variables, passed as arguments, and returned as values. To pass a function as a parameter, simply assign it to a variable of type func(paramList) returnType.

Example

Consider the following code snippet:

package main

import "fmt"

// define a function that converts an integer to a string
func convert(x int) string {
    return fmt.Sprintf("%v", x)
}

// define a function that passes a function as a parameter
func quote123(fn func(int) string) string {
    return fmt.Sprintf("%q", fn(123))
}

func main() {
    result := quote123(convert)
    fmt.Println(result) // Output: "123"
}

In this example, we define a function called convert that converts an integer to a string value. We then pass this function as a parameter to another function called quote123. The quote123 function takes a function of type func(int) string as an argument. Within the function, we call the passed-in function and pass in the value 123. The result is returned as a quoted string.

Additional Examples

You can also define and pass anonymous functions as parameters. For example:

result := quote123(func(x int) string { return fmt.Sprintf("%b", x) })
fmt.Println(result) // Output: "1111011"

In this case, we pass an anonymous function that converts an integer to its binary representation.

Functional Interfaces

Go does not have explicit functional interfaces like Java or C#. However, you can define your own types that require specific function signatures. For instance, you could define the following type:

type MyFunctionType func(int) string

This type would require any function passed as a parameter to have the following signature: func(int) string. You can then use this type to ensure that only functions with the correct signature are passed.

Conclusion

Go provides powerful mechanisms for passing functions as parameters through function closures. This allows for a great deal of flexibility and code reuse, making Go an excellent choice for applications that require higher-order functions.

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