Trait from_attr::FromAttr

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pub trait FromAttr: Sized {
    type Parser: ParseMeta + Default;

    // Required method
    fn from_parser(parser: Self::Parser, spans: &[Span]) -> Result<Self>;

    // Provided methods
    fn from_meta_list(list: &MetaList) -> Result<Option<Self>>
       where Self: AttributeIdent { ... }
    fn from_attributes(
        attrs: &[Attribute]
    ) -> Result<Option<AttrsValue<&Attribute, Self>>, AttrsValue<&Attribute, Error>>
       where Self: AttributeIdent { ... }
    fn remove_attributes(
        attrs: &mut Vec<Attribute>
    ) -> Result<Option<AttrsValue<Attribute, Self>>, AttrsValue<Attribute, Error>>
       where Self: AttributeIdent { ... }
    fn from_tokens(tokens: TokenStream) -> Result<Self> { ... }
}
Expand description

Used for conversion from Attributes, MetaList, TokenStream to values.

Instead of converting directly from Attributes, MetaList, TokenStream to values, we need to use the helper type that implements ParseMeta and Default to convert to this type first, and then convert to the value we really need.

Required Associated Types§

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type Parser: ParseMeta + Default

The helper type that implements ParseMeta and Default.

Required Methods§

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fn from_parser(parser: Self::Parser, spans: &[Span]) -> Result<Self>

Convert from Parser to values.

Provided Methods§

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fn from_meta_list(list: &MetaList) -> Result<Option<Self>>
where Self: AttributeIdent,

Convert from MetaList to values.

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fn from_attributes( attrs: &[Attribute] ) -> Result<Option<AttrsValue<&Attribute, Self>>, AttrsValue<&Attribute, Error>>
where Self: AttributeIdent,

Convert from Attributes to values.

Does not remove Attributes and is generally used to parse attributes of derive macros.

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fn remove_attributes( attrs: &mut Vec<Attribute> ) -> Result<Option<AttrsValue<Attribute, Self>>, AttrsValue<Attribute, Error>>
where Self: AttributeIdent,

Convert from Attributes to values.

Does remove Attributes and is generally used to parse attributes of attribute macros.

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fn from_tokens(tokens: TokenStream) -> Result<Self>

Convert from TokenStream to values.

Generally used for parsing TokenStream for attribute macros.

Object Safety§

This trait is not object safe.

Implementors§