Understanding the Defaults

Required/Optional Fields - Main concept

There is a concept:

• if the input model field is, for example, String (and not Option) - the field is required.
• if the input model field is Option - the field is optional;
• if there is an Default Value in the field description - the field became optional in any cases;

#[derive(MyHttpInput)]
pub struct DefaultStringQueryInputModel {
    #[http_query(name : "noDefault", description=: "Test")]
    pub no_default: String, //Required Field

    #[http_query(name = "withDefault"; description: "MyDescription", default: "MyDefault")]
    pub with_default: String, //Optional Field

    #[http_query(name : "noDefaultOpt", description=: "Test")]
    pub no_default_opt: Option<String>, //Optional Field

    #[http_query(name = "withDefaultOpt"; description: "MyDescription", default: "MyDefault")]
    pub with_default_opt: Option<String>, //Optional Field
}

Default values

A default value can be specified inside the field description as a Value for types such as:

• i8...i64;
• u8...u64;
• f32, f64
• String,
• DateTimeAsMicroseconds

Example

#[derive(MyHttpInput)]
pub struct DefaultStringQueryInputModel {
    #[http_query(name = "withDefault"; description: "MyDescription", default: "MyDefault")]
    pub with_default: String, 
}

Default with Enums

Any Enum Case can be marked as Default.

#[derive(MyHttpStringEnum)]
pub enum MyEnumModel {
    #[http_enum_case(id: 0, value:"myCase1", description = "My Case 1 Description", default)]
    Case1,

    #[http_enum_case(id: 1, description = "My Case 1 Description")]
    Case2,

    #[http_enum_case(id: 2, description = "My Case 1 Description")]
    Case3,
}

#[derive(MyHttpInput)]
pub struct MyHttpInput {
    #[http_query(name = "myEnum", description = "a", default)] // <-- Default parameter without value takes the Default case of MyEnumModel
    pub my_enum: MyEnumModel,
}

Under the hood, it generates the Default Trait and Some Auxiliary methods, which are used to create the Default Version of Enum if needed.

impl MyEnumModel {
    pub fn create_default() -> Result<Self, my_http_server::HttpFailResult> {
        Ok(Self::default())
    }
    pub fn default_as_str() -> &'static str {
        "Case1"
    }
}

impl std::default::Default for MyEnumModel {
    fn default() -> Self {
        Self::Case1
    }
}