我正在开发一个 MATLAB 类,该类存储使用tcpip
创建的接口对象,并包含一个供接口对象使用的回调函数,如以下示例所示:
classdef wsg50_mini2 < handle
properties
TCPIP
end
%PUBLIC METHODS
methods
%CONSTRUCTOR
function obj = wsg50_mini2(varargin)
fprintf('################# I am created #################n')
obj.TCPIP = tcpip('localhost',1000);
obj.TCPIP.OutputBufferSize = 3000;
obj.TCPIP.InputBufferSize = 3000;
obj.TCPIP.ByteOrder = 'littleEndian';
obj.TCPIP.Timeout = 1;
%Setting up Callbackfunction
obj.TCPIP.BytesAvailableFcnMode = 'byte';
obj.TCPIP.BytesAvailableFcnCount = 1;
obj.TCPIP.BytesAvailableFcn = {@obj.TCP_Callback, obj};
end
end
%PRIVATE METHODS
methods (Access = private)
%DESTRUCTOR
function delete(obj)
fprintf('################# Hey I am called! #################n')
instrreset
end
end
%STATIC METHODS
methods (Static)
%TCP Callback
%This function will be called if one Byte is available at the TCPIP
%buffer.
function TCP_Callback(tcpsocket,event,obj)
fprintf('Loading 1 Byte Data From Buffer.n')
end
end
end
当我清除我的类时,变量将从工作区中清除,但不调用delete
析构函数。为什么不呢?
我意识到,我的仪器在仪器控制应用程序中仍然处于活动状态。如果我从那里删除我的工具,我的delete
析构函数将被调用。
我认为这是 tcpip 类的一些奇怪行为。
听起来很像您在Instrument Control App
类中有wsg50
变量引用,在这种情况下,当您从工作区中清除变量时,因为它仍然在其他地方被引用,它不是deleted
。
让我们看一个简单的例子:
classdef myClass < handle
properties
name = '';
end
methods
function delete ( obj )
fprintf ( '%s being deletedn', obj.name );
end
end
end
右让我们运行一些代码:
var = basicClass;
var.name = '123';
如果我们清除此变量,则可以看到调用delete
:
>> clear var
being deleted
如果我们运行这段代码并在其他地方进行引用:
var = basicClass;
var.name = '123';
otherReference.var = var;
查看这两个变量,它们是相同的(如预期的那样(:
>> var
var =
myClass with properties:
name: '123'
>> otherReference.var
ans =
myClass with properties:
name: '123'
那么,如果我们clear
var
并查看其他参考,会发生什么
clear var
otherReference.var.name
>> otherReference.var
ans =
myClass with properties:
name: '123'
我们可以看到类变量是活的,因为它应该是,因为这与作为函数输入的类没有区别,当该函数完成时,该变量的本地副本将从范围中清除。
如果我们真的要删除变量,那么你可以执行以下操作,在其中显式运行析构函数方法:
var = basicClass;
var.name = '123';
otherReference.var = var;
delete(var);
otherReference.var.name
delete
行为我们提供:
123 being deleted
如果我们看一下otherReference.var
,我们会得到:
Invalid or deleted object.
这实际上将删除变量,您将看到otherReference
现在是指向无效句柄的指针。
问题是行obj.TCPIP.BytesAvailableFcn = {@obj.TCP_Callback, obj};
.引用@obj.TCP_Callback
在 tcpip 对象内创建类的实例,该对象是类本身的属性。
最简单的解决方案是清除析构函数内部的obj.TCPIP.BytesAvailableFcn = ''
并手动调用析构函数。如果代码仅由其创建者使用,则可以。
为了保持面向对象的代码完整,Wrapper-Class用于回调函数。主文件使用包装类和侦听器进行更新,如下所示。回调的设置将替换为两者的组合。然后,析构函数需要调用包装器(从回调中删除自身的实例(和侦听器的析构函数:
classdef wsg50_mini2 < handle
properties
TCPIP
TCPIPWrapper
LH
end
%PUBLIC METHODS
methods
%CONSTRUCTOR
function obj = wsg50_mini2(varargin)
fprintf('################# I am created #################n')
% Create TCPIP Object
obj.TCPIP = tcpip('localhost',1000);
% Create TCPIP Wrapper
obj.TCPIPWrapper = TCPIPWrapper(obj.TCPIP)
% Add Listener
obj.LH = listener(obj.TCPIPWrapper,'BytesAvailableFcn',@obj.onBytes);
obj.TCPIP.OutputBufferSize = 3000;
obj.TCPIP.InputBufferSize = 3000;
obj.TCPIP.ByteOrder = 'littleEndian';
obj.TCPIP.Timeout = 1;
end
end
%PRIVATE METHODS
methods (Access = private)
%DESTRUCTOR
function delete(obj)
fprintf('################# Hey I am called! #################n')
% Destroy Listener
delete(obj.LH);
% destroy Wrapper
delete(obj.TCPIPWrapper);
instrreset
end
end
%STATIC METHODS
methods (Private)
function onBytes(obj,~,~)
fprintf('Loading 1 Byte Data From Buffer.n')
end
end
end
附加包装器如下所示:
classdef TCPIPWrapper < handle
properties(Access=private)
tcpip
end
events
BytesAvailableFcn
end
methods
% tcpipCallbackWrapper Constructor
function obj = tcpipCallbackWrapper(tcpip)
disp 'CONSTRUCTED tcpipCallbackWrapper'
% Keep a reference to the tcpip object
obj.tcpip = tcpip;
% Adding this listener will result in the destructor not being
% called automatically anymore; but luckily we have myClass
% which will explicitly call it for us
obj.tcpip.BytesAvailableFcnMode = 'byte';
obj.tcpip.BytesAvailableFcnCount = 1;
obj.tcpip.BytesAvailableFcn = @obj.bytesAvailableFcn;
end
% tcpipCallbackWrapper Destructor
function delete(obj)
disp 'DESTRUCTED tcpipCallbackWrapper'
% Overwrite the callback with a new empty one, removing the
% reference from the callback to our class instance, allowing
% the instance to truly be destroyed
obj.tcpip.BytesAvailableFcn = '';
end
end
methods (Access=private)
% Callback for BytesAvailableFcn
function bytesAvailableFcn(obj,~,~)
notify(obj, 'BytesAvailableFcn');
end
end
end