我可以得到一个字段是否已经在 golang 中分配了反射

Question

我有一个结构如下：

type Demo struct{
     A string
     B string}

我有一个实例如下：

demo := Demo{A:"a"}

A的字段已显式分配值，但字段B未分配值。现在，我想知道是否存在一些方法可以通过反射获取实例A的字段？

在这里，我想获得字段A。

Answer 1

无法确定某个字段是否显式分配了一个值，但可以确定是否存在不等于该字段零值的字段。遍历字段。如果字段的值不等于字段类型的零值，则返回 true。func hasNonZeroField(s interface{}) bool {&nbsp; &nbsp; v := reflect.ValueOf(s)&nbsp; &nbsp; if v.Kind() == reflect.Ptr {&nbsp; &nbsp; &nbsp; &nbsp; v = v.Elem()&nbsp; &nbsp; }&nbsp; &nbsp; t := v.Type()&nbsp; &nbsp; for i := 0; i < t.NumField(); i++ {&nbsp; &nbsp; &nbsp; &nbsp; sf := t.Field(i)&nbsp; &nbsp; &nbsp; &nbsp; fv := v.Field(i)&nbsp; &nbsp; &nbsp; &nbsp; switch sf.Type.Kind() {&nbsp; &nbsp; &nbsp; &nbsp; case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Ptr, reflect.Slice:&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if !fv.IsNil() {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return true&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; case reflect.Struct:&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if hasNonZeroField(fv.Interface()) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return true&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; // case reflect.Array:&nbsp; &nbsp; &nbsp; &nbsp; // TODO: call recursively for array elements&nbsp; &nbsp; &nbsp; &nbsp; default:&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if reflect.Zero(sf.Type).Interface() != fv.Interface() {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return true&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }&nbsp; &nbsp; return false}在操场上运行它。