1 // Copyright 2012 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 package reflect_test 6 7 import ( 8 "fmt" 9 "io" 10 "os" 11 "reflect" 12 ) 13 14 func ExampleMakeFunc() { 15 // swap is the implementation passed to MakeFunc. 16 // It must work in terms of reflect.Values so that it is possible 17 // to write code without knowing beforehand what the types 18 // will be. 19 swap := func(in []reflect.Value) []reflect.Value { 20 return []reflect.Value{in[1], in[0]} 21 } 22 23 // makeSwap expects fptr to be a pointer to a nil function. 24 // It sets that pointer to a new function created with MakeFunc. 25 // When the function is invoked, reflect turns the arguments 26 // into Values, calls swap, and then turns swap's result slice 27 // into the values returned by the new function. 28 makeSwap := func(fptr interface{}) { 29 // fptr is a pointer to a function. 30 // Obtain the function value itself (likely nil) as a reflect.Value 31 // so that we can query its type and then set the value. 32 fn := reflect.ValueOf(fptr).Elem() 33 34 // Make a function of the right type. 35 v := reflect.MakeFunc(fn.Type(), swap) 36 37 // Assign it to the value fn represents. 38 fn.Set(v) 39 } 40 41 // Make and call a swap function for ints. 42 var intSwap func(int, int) (int, int) 43 makeSwap(&intSwap) 44 fmt.Println(intSwap(0, 1)) 45 46 // Make and call a swap function for float64s. 47 var floatSwap func(float64, float64) (float64, float64) 48 makeSwap(&floatSwap) 49 fmt.Println(floatSwap(2.72, 3.14)) 50 51 // Output: 52 // 1 0 53 // 3.14 2.72 54 } 55 56 func ExampleStructTag() { 57 type S struct { 58 F string `species:"gopher" color:"blue"` 59 } 60 61 s := S{} 62 st := reflect.TypeOf(s) 63 field := st.Field(0) 64 fmt.Println(field.Tag.Get("color"), field.Tag.Get("species")) 65 66 // Output: 67 // blue gopher 68 } 69 70 func ExampleTypeOf() { 71 // As interface types are only used for static typing, a 72 // common idiom to find the reflection Type for an interface 73 // type Foo is to use a *Foo value. 74 writerType := reflect.TypeOf((*io.Writer)(nil)).Elem() 75 76 fileType := reflect.TypeOf((*os.File)(nil)) 77 fmt.Println(fileType.Implements(writerType)) 78 79 // Output: 80 // true 81 } 82
