Trait opcua_server::callbacks::AttributeGetter

source · [−]
pub trait AttributeGetter {
    fn get(
        &mut self, 
        node_id: &NodeId, 
        timestamps_to_return: TimestampsToReturn, 
        attribute_id: AttributeId, 
        index_range: NumericRange, 
        data_encoding: &QualifiedName, 
        max_age: f64
    ) -> Result<Option<DataValue>, StatusCode>;
}
Expand description

An attribute getter trait is used to obtain the data value associated with the particular attribute id This allows server implementations to supply a value on demand, usually in response to a polling action such as a monitored item in a subscription.

node_id is the node to which the node belongs attribute_id is the attribute of the node to fetch a value for

Use max_age according to the OPC UA Part 4, Table 52 specification to determine how to return a value:

  • 0 = a new value
  • time in ms for a value less than the specified age
  • i32::max() or higher to fetch a cached value.

Required methods

Returns a data value of the specified attribute or none.

Implementors