英文:
Go, %v format invoking String() for a nested struct
问题
在下面的代码中，我期望fmt.Printf("%v\n", a)会调用其类型为myTypeB的成员的String()方法，但实际上并没有发生。为什么会这样？
package main
import "fmt"
type myTypeA struct {
b myTypeB
}
type myTypeB struct {
c string
d int
}
func (b myTypeB) String() string {
return "myTypeB custom"
}
func main() {
a:= myTypeA{myTypeB{"hello", 1}};
b:= myTypeB{"hello", 1}
fmt.Printf("%v\n", a)
fmt.Printf("%v\n", b)
}
英文:
In the following code, I would expect fmt.Printf("%v\n", a) to invoke String() of its member of type myTypeB, but this is not happening ? Why ?
package main
import "fmt"
type myTypeA struct {
b myTypeB
}
type myTypeB struct {
c string
d int
}
func (b myTypeB) String() string {
return "myTypeB custom"
}
func main() {
a:= myTypeA{myTypeB{"hello", 1}};
b:= myTypeB{"hello", 1}
fmt.Printf("%v\n", a)
fmt.Printf("%v\n", b)
}
答案1
得分: 3
fmt不会递归地查找fmt.Stringer。
如果参数是一个fmt.Stringer，它将调用String()方法并打印结果。如果没有String()方法，fmt将使用反射迭代字段以获取值。
英文:
fmt doesn't look for fmt.Stringer recursively.
If the argument is a fmt.Stringer, it will invoke the String() method, and print the results. If it doesn't have a String() method, fmt will iterate over the fields using reflection to obtain the value.
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