英文:
Check empty struct that have array fields
问题
我有一个嵌套的（非嵌入式）结构体，其中一些字段类型是数组。
如何检查此结构体的实例是否为空？（不使用迭代！）
请注意，不能使用StructIns == (Struct{})或空实例来进行比较！这段代码会出现以下错误：
invalid operation: user == model.User literal (struct containing model.Configs cannot be compared)
user.Configs.TspConfigs:
type TspConfigs struct {
Flights []Flights `form:"flights" json:"flights"`
Tours []Tours `form:"tours" json:"tours"`
Insurances []Insurances`form:"insurances" json:"insurances"`
Hotels []Hotels `form:"hotels" json:"hotels"`
}
英文:
I have a nested (not embedded) struct for which some of field types are arrays.
How can I check if an instance of this struct is empty? (not using iteration!!)
Note that there can't use StructIns == (Struct{}) or by an empty instance! This code have this error:
invalid operation: user == model.User literal (struct containing model.Configs cannot be compared)
user.Configs.TspConfigs:
type TspConfigs struct {
Flights []Flights `form:"flights" json:"flights"`
Tours []Tours `form:"tours" json:"tours"`
Insurances []Insurances`form:"insurances" json:"insurances"`
Hotels []Hotels `form:"hotels" json:"hotels"`
}
答案1
得分: 3
这些是切片（slices），而不是数组（arrays）。强调一下，数组是可比较的，但切片不是。请参考《规范：比较运算符》。由于切片不可比较，由它们组成的结构体（具有切片类型字段的结构体）也不可比较。
你可以使用reflect.DeepEqual()来进行比较。例如：
type Foo struct {
A []int
B []string
}
f := Foo{}
fmt.Println("Zero:", reflect.DeepEqual(f, Foo{}))
f.A = []int{1}
fmt.Println("Zero:", reflect.DeepEqual(f, Foo{}))
输出结果（在Go Playground上尝试）：
Zero: true
Zero: false
英文:
Those are slices, not arrays. It's important to emphasize as arrays are comparable but slices are not. See Spec: Comparision operators. And since slices are not comparable, structs composed of them (structs with fields having slice types) are also not comparable.
You may use reflect.DeepEqual() for this. Example:
type Foo struct {
A []int
B []string
}
f := Foo{}
fmt.Println("Zero:", reflect.DeepEqual(f, Foo{}))
f.A = []int{1}
fmt.Println("Zero:", reflect.DeepEqual(f, Foo{}))
Output (try it on the Go Playground):
Zero: true
Zero: false
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