当给定的数据校验规则中不包含 required* 规则时，表示该规则不是一个必须规则，当属性值为 nil 或者 空字符串 时，将会忽略其校验。

示例1，空字符串

type Params struct {
    Page      int    `v:"required|min:1         # page is required"`
    Size      int    `v:"required|between:1,100 # size is required"`
    ProjectId string `v:"between:1,10000        # project id must between :min, :max"`
}
obj := &Params{
    Page: 1,
    Size: 10,
}
err := gvalid.CheckStruct(context.TODO(), obj, nil)
fmt.Println(err)
// Output:
// <nil>

示例2，空指针属性

type Params struct {
    Page      int       `v:"required|min:1         # page is required"`
    Size      int       `v:"required|between:1,100 # size is required"`
    ProjectId *gvar.Var `v:"between:1,10000        # project id must between :min, :max"`
}
obj := &Params{
    Page: 1,
    Size: 10,
}
err := gvalid.CheckStruct(context.TODO(), obj, nil)
fmt.Println(err)
// Output:
// <nil>

示例3，空整型属性

需要注意的是，如果键值为 0 或者 false，参数值将仍然会被校验。

type Params struct {
    Page      int `v:"required|min:1         # page is required"`
    Size      int `v:"required|between:1,100 # size is required"`
    ProjectId int `v:"between:1,10000        # project id must between :min, :max"`
}
obj := &Params{
    Page: 1,
    Size: 10,
}
err := gvalid.CheckStruct(context.TODO(), obj, nil)
fmt.Println(err)
// Output:
// project id must between 1, 10000