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For the release documentation, please see docs.rs, instead.

Trait tracing::field::AsField

source ·
pub trait AsField: Sealed {
    // Required method
    fn as_field(&self, metadata: &Metadata<'_>) -> Option<Field>;
Expand description

Trait implemented to allow a type to be used as a field key.

Note: Although this is implemented for both the Field type and any type that can be borrowed as an &str, only Field allows O(1) access. Indexing a field with a string results in an iterative search that performs string comparisons. Thus, if possible, once the key for a field is known, it should be used whenever possible.

Required Methods§


fn as_field(&self, metadata: &Metadata<'_>) -> Option<Field>

Attempts to convert &self into a Field with the specified metadata.

If metadata defines this field, then the field is returned. Otherwise, this returns None.

Implementations on Foreign Types§


impl AsField for str


fn as_field(&self, metadata: &Metadata<'_>) -> Option<Field>



impl AsField for Field


impl<'a> AsField for &'a Field