Type Assertion(断言)是用于interface value的一种操作,语法是x.(T),x是interface type的表达式,而T是asserted type,被断言的类型。举个例子看一下基本使用: func main() { var demo interface{} = "Golang梦工厂" str := demo.(string) fmt.Printf("value
_, isCorrectType := v.(map[string]string)if!isCorrectType { fmt.Printf("incorrect type")return} } Output: [no output] The statementv.(map[string]string)is a type assertion, not a cast. The Go Programming Language Specification Type assertions For an expressionxof interface type and a t...
The statementv.(map[string]string)is a type assertion, not a cast. The Go Programming Language Specification Type assertions For an expressionxof interface type and a typeT, the primary expression x.(T) 1. asserts thatxis notniland that the value stored inxis of typeT. The notationx.(...
如果不是string类型，会发生panic：panic:interfaceconversion:interface{}isint,notstring2 反射反射位于rel...
type = struct runtime.iface { runtime.itab *tab; void *data; } // itable 相关类型 >>> ptype b.tab type = struct runtime.itab { // 接口相关信息 runtime.interfacetype *inter; // 构造类型 runtime._type *_type; uint32 hash; ...
switch n := v.(type) { case *A: n.Add() case *B: n.Add() } } for i := 0; i < b.N; i++ { v := new(A) switchFunc(v) } } func BenchmarkInterface1(b *testing.B) { switchFunc := func(v InterfaceA) { switch v.Name() { ...
variinterface{}// 默认是 nil 值_=i.(interface{})// panic_=i.(string)// panic: interface conversion: interface {} is nil, not string 如果能知道所有预知的类型就不需要断言了,处理起来也会更叫高效、可靠,如何得到类型呢? funccaseType(whatinterface{}){switchwhat.(type){caseint:what=what.(in...
panic: interface conversion: interface {} is map[string]interface {}, not *main.ClickEvent 也就是说json直接被反序列化成了map[string]interface {},似乎更糟了。 这里有一种解决方案,就是在unmarshalEvent函数中先反序列化为Event,然后再根据其类型反序列化为其他类型。代码如下: func main() { jsonStr...
type VowelsFinder interface { FindVowels() []rune } type MyString string//MyString implements VowelsFinder func (ms MyString) FindVowels() []rune { var vowels []runefor_, rune :=range ms {ifrune =='a'|| rune =='e'|| rune =='i'|| rune =='o'|| rune =='u'{ ...
typestringerstruct{ datastring } functest1(){ stringer s t :="hello world" ReadAndClose(s, t) } functest2(){ stringer s ToString(s) } 函数test1 中由于我们的 stringer 数据结构并没有实现 Read 和 Close 函数,此处会引起编译时的报错,而 test2 中由于使用 interface{} 编译器不会它为绑定任何静...