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Class: matlab.DiscreteEventSystem
Package: matlab

Define first-in first-out (FIFO) queue storage


storage = queueFIFO(entityType,capacity)


storage = queueFIFO(entityType,capacity) defines a FIFO queue storage element. Use this function when implementing the getEntityStorageImpl method.


This page describes the queueFIFO method to create a custom discrete-event system block. See Entity Queue block provided by the SimEvents® library to use a queue with FIFO sorting policy.

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.

Output Arguments

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Queue storage that contains entities and sorts them in FIFO order.


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Specify FIFO queue entity storage for the discrete-event system object.

% Define a storage element as a FIFO queue
% - Entities in the queue are sorted in First-In-First-Out (FIFO) order
% - Queue can store entities of type 'myEntity'
% - Queue can store no more than 25 entities
storage = obj.queueFIFO('myEntity', 25); 

This example shows how to use discrete-event System object™ methods to create a custom entity storage block that has one input port, one output port, and one storage element. The discrete-event System object is the instantiation of the matlab.DiscreteEventSystem class, which allows you to use the implementation and service methods provided by this class. Then, you use the MATLAB Discrete-Event System block to integrate the System object into a SimEvents model. The custom MATLAB Discrete-Event System block accepts an entity from its input port and forwards it to its output port with a specified delay. For more information, see Delay Entities with a Custom Entity Storage Block.

classdef CustomEntityStorageBlock < matlab.DiscreteEventSystem
    % A custom entity storage block with one input, one output, and one storage. 
    % Nontunable properties 
    properties (Nontunable)
    % Capacity
        Capacity = 1;
    % Delay
    methods (Access=protected)        
        function num = getNumInputsImpl(~)
            num = 1;
        function num = getNumOutputsImpl(~)
            num = 1;
        function entityTypes = getEntityTypesImpl(obj)
            entityTypes = obj.entityType('Car');
        function [inputTypes,outputTypes] = getEntityPortsImpl(obj)
            inputTypes = {'Car'};
            outputTypes = {'Car'};

        function [storageSpecs, I, O] = getEntityStorageImpl(obj)
            storageSpecs = obj.queueFIFO('Car', obj.Capacity);
            I = 1;
            O = 1;
        function [entity,event] = CarEntry(obj,storage,entity,source)
            % Specify event actions when entity enters storage.
             event = obj.eventForward('output', 1, obj.Delay);
Introduced in R2016a