先来一个返回指针的测试,结果跟想象一样
type A map[int]string type B struct { A c int } func main() { b := B{make(A), 10} NewB := func() *B { return &b } c := NewB() c.c = 100 c.A[1] = "3" fmt.Println(b, c) } /* output {map[1:3] 100} &{map[1:3] 100} */再试试直接返回值，这下的输出和想象中不一样了
type A map[int]string type B struct { A c int } func main() { a := B{make(A), 10} b := B{make(A), 10} NewB := func() B { return b } c := NewB() c.c = 100 c.A[1] = "3" // c[1]="3" invalid operation: c[1] (type B does not support indexing) fmt.Println(a, b, c) } /* output {map[] 10} {map[1:3] 10} {map[1:3] 100} */为什么呢，再试试
type A map[int]string type B struct { A c int } func main() { a := make(A) NewA := func() A { return a } b := NewA() b[1] = "10" fmt.Println(a, b) } /* output map[1:10] map[1:10] */ 这样就编译不过了 func main() { a := make(A) NewA := func() *A { return &a } b := NewA() b[1] = "10" //invalid operation: b[1] (type *A does not support indexing) fmt.Println(a, b) }go 语言中map,slice都是指针类型，以值的形式返回struct的时候只是把map对应的指针拷贝了
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