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queuePriority

Class: matlab.DiscreteEventSystem
Namespace: matlab

Define priority queue storage

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Syntax

storage=queuePriority(entityType,capacity,key,order)

Description

storage=queuePriority(entityType,capacity,key,order) defines a priority queue that sorts entities by custom attribute. Use this function when implementing the getEntityStorageImpl method.

Input Arguments

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Type of entities that the new storage element works with.

Maximum number of entities that the storage can contain, specified as a double.

Name of the attribute that is used as the key for sorting.

Direction of sorting. Specify 'ascending' if you want entities with smaller key values to appear in front of the queue. Specify 'descending' if you want entities with greater key values to appear in front of the queue.

Output Arguments

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Queue storage element that contains entities and sorts them using a custom attribute.

Examples

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Define storage element as a priority queue.

% Define a storage element as a priority queue        
% - Queue sorts entities using a specific attribute of the entities
% - Queue can store entities of type 'myEntity'
% - Queue can store no more than 25 entities
% - Queue uses the attribute 'age' to sort entities
% - Sorting direction is 'ascending', resulting entities with
%   smaller 'age' attribute values to appear in front of the queue
storage = obj.queuePriority('myEntity', 25, 'age', 'ascending');

In this example, a custom block allows entities to enter its storage element through its input port. The storage element is a priority queue that sorts the entities based on their Diameter attribute in ascending order. Every entity entry to the block's storage invokes an iteration event to display the diameter and the position of each entity in the storage.

For more information, see Create a Custom Entity Storage Block with Iteration Event.

classdef CustomEntityStorageBlockIteration < matlab.DiscreteEventSystem
    
    % A custom entity storage block with one input port and one storage element. 
    
    % Nontunable properties 
    properties (Nontunable)
        % Capacity
        Capacity = 5;
    end
    % Create the storage element with one input and one storage.
    methods (Access=protected)

        function num = getNumInputsImpl(obj)
            num = 1;
        end
        
        function num = getNumOutputsImpl(obj)
            num = 0;
        end
        
        function entityTypes = getEntityTypesImpl(obj)
            entityType1 = obj.entityType('Wheel');
            entityTypes = entityType1;
        end
        
        function [inputTypes,outputTypes] = getEntityPortsImpl(obj)
            inputTypes = {'Wheel'};
            outputTypes={};
            
        end
        
        function [storageSpecs, I, O] = getEntityStorageImpl(obj)
            storageSpecs = obj.queuePriority('Wheel',obj.Capacity, 'Diameter','ascending');
            I = 1;
            O = [];
            
        end
        
    end
    % Entity entry event action
    methods 

        function [entity, event] = WheelEntry(obj,storage,entity, source)
            % Entity entry invokes an iterate event.      
            event = obj.eventIterate(1, '');
        end

        % The itarate event action
        function [entity,event,next] = WheelIterate(obj,storage,entity,tag,cur)
            % Display wheel id, position in the storage, and diameter.
            coder.extrinsic('fprintf');
            fprintf('Wheel id %d, Current position %d, Diameter %d\n', ...
                entity.sys.id, cur.position, entity.data.Diameter);
            if cur.size == cur.position 
                fprintf('End of Iteration \n')
            end
            next = true;
            event=[];
        end
        
    end

end

Version History

Introduced in R2016a

See Also

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