read_existing_point, read_point

Arguments

Returns

The value of a point in the Cascade DataHub. If the point is unavailable then nil is returned. For read_existing_point, if the point does not exist than nil is returned. For read_point, if the point does not exist then the point is created and a default value is returned.

Description

These functions makes a call to the Cascade DataHub to retrieve the point whose name is the same as the symbol. If the point does not exist in the datahub, read_existing_point returns nil and does not create the point. read_point will create a point in the datahub if necessary, whose value and confidence are both zero. If the point name is pre-qualified with a domain name and a colon (:), this function will search that domain's datahub rather than the datahub for the default domain.

Example

This example uses data points entered in the write_point reference entry example.

    Gamma> init_ipc("reader","rq");
    t
    Gamma> read_point(#my);
    600
    Gamma> read_point(#dog);
    130
    Gamma> read_point(#has);
    140
    Gamma> read_point(#fleas);
    150
    Gamma> read_existing_point(#cat);
    nil
    Gamma> read_point(#cat);
    0
    Gamma> 
    		

See Also

register_point, write_point