是否可以即时将方法添加到MATLAB类? [英] Is it possible to add methods on the fly to MATLAB classes?

问题描述

编写dynamicprops的子类使我可以向对象动态添加属性:

Writing a subclass of dynamicprops allows to me to add properties dynamically to an object:

addprop(obj, 'new_prop')

这很棒，但是我也很想为这些属性即时创建set / get函数.或适用于这些动态属性的分析功能.

This is great, but I would also love to create set / get functions for these properties on the fly. Or analysis functions that work on these dynamic properties.

到目前为止，我对Matlab的经验是，一旦我创建了一个类的实例，就不可能添加新的方法.这非常麻烦，因为我的对象可能包含很多数据，每次我想添加新方法时都必须重新加载这些数据(因为必须执行clear classes).

My experience with Matlab has been so far, that once I create an instance of a class, adding new methods is not possible. That is very cumbersome, because my object may contain a lot of data, which I'll have to re-load every time that I want to add a new method (because I have to do clear classes).

那么有没有一种动态添加方法的方法?

So is there a way to add methods on the fly?

推荐答案

您不能像添加动态属性那样添加方法.但是，有两种方法可以在开发过程中实施新方法，而无需每次都重新加载数据.

You cannot add methods like you add dynamic properties. However, there are two ways for implementing new methods during development that won't require you to re-load the data every time.

(1)我将标准方法编写为单独的函数，并在开发过程中将其称为myMethod(obj).一旦确定它们是稳定的，就将它们的签名添加到类定义文件中-当然，这需要一个clear classes，但这是一个大大的延迟，并且您可能会不时地关闭Matlab ，无论如何.

(1) I write standard methods as separate functions, and call them as myMethod(obj) during development. Once I'm sure they're stable, I add their signature into the class definition file - this requires a clear classes, of course, but it is a much delayed one, and from time to time you may have to shut down Matlab, anyway.

(2)使用set/get方法，事情有些棘手.如果使用dynamicprops添加新属性，则还可以指定其set/get方法(但是，这些方法/函数很可能希望接收属性名称，以便它们知道要引用的内容):

(2) With set/get methods, things are a little trickier. If you are using dynamicprops to add new properties, you can also specify their set/get methods, however (most likely, these methods/functions will want to receive the name of the property so that they know what to refer to):

addprop(obj,'new_prop');
prop = findprop(obj,'new_prop');
prop.SetMethod = @(obj,val)yourCustomSetMethod(obj,val,'new_prop')

编辑

(2.1)这是一个示例，说明如何设置隐藏属性以存储和检索结果(基于 jmlopez的答案).显然，如果您对自己的实际设计有个更好的了解，可以大大改善这一点

(2.1) Here's an example of how to set up a hidden property to store and retrieve results (based on jmlopez' answer). Obviously this can be improved a lot if you have a better idea what you're actually designing

classdef myDynamicClass < dynamicprops
    properties (Hidden)
        name %# class name
        store %# structure that stores the values of the dynamic properties
    end
    methods
        function self = myDynamicClass(clsname, varargin)
            % self = myDynamicClass(clsname, propname, type)
            % here type is a handle to a basic datatype.
            self.name_ = clsname;
            for i=1:2:length(varargin)
                key = varargin{i};
                addprop(self, key);
                prop = findprop(self, key);
                prop.SetMethod = @(obj,val)myDynamicClass.setMethod(obj,val,key);
                prop.GetMethod = @(obj)myDynamicClass.getMethod(obj,key);
            end
        end
        function out = classname(self)
            out = self.name_;
        end
    end
    methods (Static, Hidden) %# you may want to put these in a separate fcn instead
        function setMethod(self,val,key)
           %# have a generic test, for example, force nonempty double
           validateattributes(val,{'double'},{'nonempty'}); %# will error if not double or if empty

           %# store
           self.store.(key) = val;

        end
        function val = getMethod(self,key)
           %# check whether the property exists already, return NaN otherwise
           %# could also use this to load from file if the data is not supposed to be loaded on construction 
           if isfield(self.store,key)
              val = self.store.(key);
           else
              val = NaN;
           end
        end
    end
end

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