53 lines
1.5 KiB
Go
53 lines
1.5 KiB
Go
// Copyright 2012 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package reflect_test
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import (
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"fmt"
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"reflect"
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)
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func ExampleMakeFunc() {
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// swap is the implementation passed to MakeFunc.
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// It must work in terms of reflect.Values so that it is possible
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// to write code without knowing beforehand what the types
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// will be.
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swap := func(in []reflect.Value) []reflect.Value {
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return []reflect.Value{in[1], in[0]}
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}
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// makeSwap expects fptr to be a pointer to a nil function.
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// It sets that pointer to a new function created with MakeFunc.
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// When the function is invoked, reflect turns the arguments
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// into Values, calls swap, and then turns swap's result slice
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// into the values returned by the new function.
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makeSwap := func(fptr interface{}) {
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// fptr is a pointer to a function.
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// Obtain the function value itself (likely nil) as a reflect.Value
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// so that we can query its type and then set the value.
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fn := reflect.ValueOf(fptr).Elem()
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// Make a function of the right type.
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v := reflect.MakeFunc(fn.Type(), swap)
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// Assign it to the value fn represents.
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fn.Set(v)
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}
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// Make and call a swap function for ints.
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var intSwap func(int, int) (int, int)
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makeSwap(&intSwap)
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fmt.Println(intSwap(0, 1))
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// Make and call a swap function for float64s.
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var floatSwap func(float64, float64) (float64, float64)
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makeSwap(&floatSwap)
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fmt.Println(floatSwap(2.72, 3.14))
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// Output:
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// 1 0
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// 3.14 2.72
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}
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