英文:
Can I write a Go method that operates on a struct with arbitrary number of fields?
问题
我有一个Go结构体，看起来像这样：
type myStruct struct {
A bool
B bool
C bool
}
我想编写一个方法，将布尔值从true翻转为false，反之亦然。但我不想为字段A、B和C重复相同的代码3次。我想要写一个循环。
我考虑的代码如下：
func (m *myStruct) flipBools() {
r := reflect.ValueOf(*m)
for i := 0; i < r.NumField(); i++ {
// 在这里写什么？
}
}
但我不知道在循环内部应该写什么。这可行吗？我意识到对于像Go这样的强类型语言来说，这是一个很高的要求。
英文:
I have a Go struct that looks like this:
type myStruct struct {
A bool
B bool
C bool
}
I want to write a method that flips the bool values from true to false and vice-versa. But I don't want to repeat the same code 3 times for fields A, B & C. I want to write a loop.
I'm thinking something like this:
func (m *myStruct) flipBools() {
r := reflect.ValueOf(*m)
for i := 0; i < r.NumField(); i++ {
// WHAT GOES HERE?
}
}
But I don't know what to put inside the loop. Can it be done? I realize this is a tall order for a strongly typed language like Go.
答案1
得分: 3
不需要反射。
func (m *myStruct) flipBools() {
ps := []*bool{&m.A, &m.B, &m.C}
for _, p := range ps {
*p = !*p
}
}
你甚至可以将逻辑提取到一个可变参数的函数中，并且可以重复使用，如果你想的话：
func flipBools(ps ...*bool) {
for _, p := range ps {
*p = !*p
}
}
func (m *myStruct) flipBools() {
flipBools(&m.A, &m.B, &m.C)
}
英文:
No need for reflection.
func (m *myStruct) flipBools() {
ps := []*bool{&m.A, &m.B, &m.C}
for _, p := range ps {
*p = !*p
}
}
https://play.golang.org/p/RrCo4Kph-hl
You can even extract the logic into a variadic func and have it be re-used, if you want to:
func flipBools(ps ...*bool) {
for _, p := range ps {
*p = !*p
}
}
func (m *myStruct) flipBools() {
flipBools(&m.A, &m.B, &m.C)
}
答案2
得分: 3
为了实际回答这个问题：是的，这是可能的（即使不是特别明智）。以下是实现的代码：
func (m *myStruct) flipBools() {
r := reflect.ValueOf(m).Elem()
for i := 0; i < r.NumField(); i++ {
fld := r.Field(i)
if fld.Kind() == reflect.Bool {
fld.SetBool(!fld.Bool())
} // 可选：否则，做其他操作？
}
}
内部循环实际上很简单；唯一需要修复的是使用 reflect.ValueOf(*m) 会得到一个不可寻址的值，无法设置其字段；而 reflect.ValueOf(m).Elem() 通过指针访问结构体，这样就可以正常工作了。
英文:
In the spirit of actually answering the question: yes, it's possible (even if it's not particularly wise). This works:
func (m *myStruct) flipBools() {
r := reflect.ValueOf(m).Elem()
for i := 0; i < r.NumField(); i++ {
fld := r.Field(i)
if fld.Kind() == reflect.Bool {
fld.SetBool(!fld.Bool())
} // optional: else, do something else?
}
}
The inner loop is actually pretty easy; the only thing that needed fixing was that using reflect.ValueOf(*m) leaves you with an un-addressable value that can't have its fields set; reflect.ValueOf(m).Elem() accesses the struct through the pointer, which works fine.
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