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Selecting Functions Based on Return or Parameter Types in Go
In Go, it is possible to programmatically select functions based on their return or parameter types. This can be useful when you have a collection of functions and need to filter out only those that meet certain criteria.
The Go standard library provides the reflect package, which allows you to manipulate and inspect types. To select functions based on their types, you can use the following steps:
Here is an example that demonstrates how to select functions that take an int as a parameter or return an int:
<code class="go">package main import ( "fmt" "reflect" ) func main() { funcs := make([]interface{}, 3, 3) // Using interface{} to allow any kind of function funcs[0] = func(a int) int { return a + 1 } // Good: takes int, returns int funcs[1] = func(a string) int { return len(a) } // Good: returns int funcs[2] = func(a string) string { return ":(" } // Bad: returns string for _, fi := range funcs { f := reflect.ValueOf(fi) functype := f.Type() good := false for i := 0; i < functype.NumIn(); i++ { if functype.In(i).String() == "int" { good = true // Yes, there is an int input break } } for i := 0; i < functype.NumOut(); i++ { if functype.Out(i).String() == "int" { good = true // Yes, there is an int output break } } if good { fmt.Println(f) } } }</code>
This code showcases the use of reflect to inspect function types and filter out functions that meet the desired criteria. It demonstrates how to select functions that take ints as inputs or return ints as outputs.
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