struct{int}和struct{int int}有什么区别？

Question

struct{int}和struct{int int}有什么区别？

5

除了它们不被视为等同之外，这两个结构体有什么区别？

package main
import "fmt"
func main() {
    a := struct{int}{1}
    b := struct{int int}{1}
    fmt.Println(a,b)
    a.int=2
    b.int=a.int
    fmt.Println(a,b)
    //a = b
}

它们看起来一样：

$ go run a.go 
{1} {1}
{2} {2}

如果您取消注释a = b，它会显示：

$ go run a.go 
# command-line-arguments
./a.go:10: cannot use b (type struct { int int }) as type struct { int } in assignment

然而，struct{a,b int}和struct{a int;b int}是等价的：

package main

func main() {
    a := struct{a,b int}{1,2}
    b := struct{a int;b int}{1,2}
    a = b
    b = a
}

?

- Dog

1个回答

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- peterSO · Accepted Answer

"struct { int }"是一个具有匿名类型为int的结构体。

"struct { int int }"是一个具有类型为int且命名为int的字段的结构体。 int不是一个关键字，可以作为标识符使用。

两个结构体类型不相同；对应的字段没有相同的名称。

声明一个带有类型但没有显式字段名称的字段是一个匿名字段，未限定的类型名称充当匿名字段名称。因此，字段名称a.int和b.int是有效的。例如：

a := struct{ int }{1}
b := struct{ int int }{1}
a.int = 2
b.int = a.int

The Go Programming Language Specification

Struct types

A struct is a sequence of named elements, called fields, each of which has a name and a type. Field names may be specified explicitly (IdentifierList) or implicitly (AnonymousField). Within a struct, non-blank field names must be unique.
StructType     = "struct" "{" { FieldDecl ";" } "}" .
FieldDecl      = (IdentifierList Type | AnonymousField) [ Tag ] .
AnonymousField = [ "*" ] TypeName .
A field declared with a type but no explicit field name is an anonymous field, also called an embedded field or an embedding of the type in the struct. An embedded type must be specified as a type name T or as a pointer to a non-interface type name *T, and T itself may not be a pointer type. The unqualified type name acts as the field name.

Keywords

The following keywords are reserved and may not be used as identifiers.
break        default      func         interface    select
case         defer        go           map          struct
chan         else         goto         package      switch
const        fallthrough  if           range        type
continue     for          import       return       var
Type identity

Two struct types are identical if they have the same sequence of fields, and if corresponding fields have the same names, and identical types, and identical tags. Two anonymous fields are considered to have the same name. Lower-case field names from different packages are always different.