Attribute

Sidre Attribute objects enable users to attach metadata (strings and values) to Sidre views to support queries (e.g., search for views with a given attribute name), outputting data for a subset of views to files, and other ways an application may need to selectively process views in a Sidre data hierarchy.

An attribute is created with a string name and a default scalar or string value. A default value can be changed later as needed.

Note

• Attribute objects can only be created and destroyed using DataStore class methods. The Attribute class constructor and destructor are private (see DataStore).

• Each Attribute object has a unique name and integer identifier. Either can be used to retrieve an Attribute object from a DataStore object..

Each Sidre view inherits all attributes contained in a datastore with their default strings or values. Then, an application may explicitly set any attribute on a view. The application may also query the value of a view attribute, query whether the attribute was explicitly set, or set the attribute back to its default value. See View for more information about View objects.

The Attribute class provides the following operations:

• Retrieve the name and unique id of an attribute

• Set the scalar or string value of an attribute

• Get the type of an attribute’s scalar value

One can iterate through the attributes in the datastore using either “range-for” or iterator syntax:

// 'range-for' syntax
for(auto& attr: datastore->attributes()) { /* ... */ }

// 'iterator' syntax:
for(auto it = datastore->attributes().begin(),
      itEnd = datastore->attributes().end(); it != itEnd; ++it)
{
  auto& attr = *it;
  /* ... */
}