Derive Macro under::FromForm

source · 
#[derive(FromForm)]
{
    // Attributes available to this derive:
    #[form]
}
Expand description

Automatically derive FromForm from a struct.

Note that this requires a struct - as x-www-form-urlencoded is a key-value format, there is no way to derive FromForm for a tuple or enum. Thus, there must be keys. However, for tuple structs, the keys can be specified with the form attribute.

The form attribute currently accepts these parameters:

  • rename_all = "value" - this may only be specified on the whole struct. If it is specified, the given transformation is applied to all field names, if they are not individually renamed. Valid values are "snake_case", "camelCase", "PascalCase", "SCREAMING_SNAKE_CASE", "kebab-case", "SCREAMING-KEBAB-CASE", "lowercase", and "uppercase".
  • rename = "value" - this may only be specified on a field. If it is specified, the given name is used instead of the field name. This is useful for when the field name is not a valid identifier, or when the field name is not the same as the key in the form.
  • alias = "value" - this may only be specified on a field. If it is specified, the given name is used as an alias for the field. This is in addition to, not instead of, the field name; if you want instead of, use rename. This can be specified multiple times to add multiple aliases.
  • default - this may only be specified on a field. If it is specified, the field is optional; if it is not present in the form, the default value is used (through Default::default).
  • default = "value" - similar to above, but it uses the function specified by value (as a path) to get the default value. This is incompatible with optional and multiple.
  • optional - this may only be specified on a field. If it is specified, the field is optional; if it is not present in the form, the field is skipped. It is expected that the type of this field is Option<T>. This is different from default in how the field is handled: default will use the default value of the type, while optional will skip the field entirely. This is incompatible with default and multiple.
  • multiple - this may only be specified on a field. If it is specified, the field is a multiple field; it is expected that the type of this field implements FromFieldMultiple instead of FromFieldValue. It pushes the inner value every time the key is encountered. This is incompatible with default and optional.
  • parse_with = "value" - this may only be specified on a field. If it is specified, the field is parsed with the given function. The function must be a path to a function that takes a &str and returns a Result<T, E>, where T is the type of the field and E is the error type.