Matlab OOP从对象数组访问属性 [英] Matlab OOP accessing properties from an object array

问题描述

Matlab的新功能来自C/C ++……

New to Matlab come from C/C++......

我有一个对象数组，我正在尝试访问数组中每个对象的值，并将它们连接到一个变量中.

I have an array of objects and I'm trying to access the values of every single object in the array and concatenate them into one variable.

Class sample 
   properties(GetAccess = 'public', SetAccess ='public')
     ID;
     Value;
   end

   methods 
        function obj = sample(id, value)
            obj.ID = id;
            obj.Value = value;
         end
   end
end 

然后我创建一个包含一些对象的矩阵.

Then I make an matrix containing some of the objects.

x = sample.empty(3,0);
x(1) = sample(1,3);
x(2) = sample(1,4);
x(3) = sample(1,5);

然后，我想从对象中获取所有值并将它们存储到新数组中.

Then I want to get all the values from the objects and store them into a new array.

y = x(:).Value;

但是这失败了，仅将x(3)的值放入y .....和:

This however fails and only puts the value of x(3) into y..... and:

y(:) = x(:).Value; 

引发错误.

任何帮助将不胜感激.我知道我可以使用循环来做到这一点，但我正在尝试以最快，最有效的方式做到这一点.

Any help would be appreciated. I know I could do this with loops but I'm trying to do it in the fastest and most efficient way.

推荐答案

简单但不直观

y=[x.Value]

为什么? x.Value不是内存的连续块，因此不能直接分配给数组.调用x.Value依次从每个x对象返回Value数据成员. Matlab将此视为单独的操作.通过将调用括在[]中，您将告诉matlab通过串联每个结果来制定一个连续的数组.然后可以将其分配给双精度数组y.

Why? Well x.Value is not a contiguous block of memory, so cannot be directly assigned to an array. Calling x.Value returns the Value data member from each x object in turn. Matlab treats this as separate operations. By enclosing the call in [] you are telling matlab to formulate a contiguous array by concatenating each result. This can then be assigned to an array of doubles, y.

关于您的评论，如果x在不同对象中的长度不同，则上述代码可以正常工作，即

Regarding your comment, the above code works fine if x is of different length in different objects i.e. . .

x(1) = sample(1,3);
x(2) = sample(1,[4 5 6]);
x(3) = sample(1,[20 10]);

然后

>> [x.Value]

ans =

     3     4     5     6    20    10

如果您想让'y'是一个参差不齐的末端向量，例如C ++中的向量，则需要使用单元格数组表示法(大括号)

If you mean you want 'y' to be a ragged ended vector like is possible with a vector of vectors in C++, you need to use cell array notation (curly braces)

>> y = {x.Value}

y = 

    [3]    [1x3 double]    [1x2 double]

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