表中值类的表示

Question

如果我有一个像这样的值类:

classdef MyVal
properties
foo
end
methods 
function self = MyVal(varargin)
if nargin > 0
self.foo = varargin{1};
end
end
end
end

在表中使用:

foo(1) = MyVal(1); foo(2) = MyVal(2);
t = table(foo')

输出为:

t =
2×1 table
Var1    
___________
[1×1 MyVal]
[1×1 MyVal]

是否有任何方法必须在MyVal(或表的任何属性)中定义，允许更改表中值的表示?我不想转换传递给table的数据，因为我想在表中索引时检索MyVal的实例。

Answer 1

您可以为table创建自定义包装器。这有点笨拙，因为MATLAB不允许您继承table类，但通过重载subsref和subsasgn操作符，您可以获得大部分功能……

我把这个类包含在这个答案的底部，因为它有点长，用法看起来像这样:

>> foo(1) = MyVal(1); foo(2) = MyVal(2);
>> t = MyTable(foo') % Omitting the ";" calls our overloaded "disp" function
t = 
Var1
____
1   
2   

您也可以使用t.numeric来提取数字数据(即foo属性以及其他数据)，尽管我怀疑您将需要使用table2array来使用uitable，就像您使用正常的table一样。

classdef MyTable
properties ( Access = private )
table_
end
properties ( Dependent = true )
numeric
end
methods % Constructor and getter
function obj = MyTable( varargin )
% Store as a normal table internally
obj.table_ = table( varargin{:} );
end 
function num = get.numeric( obj )
% By calling obj.numeric, output the table but with MyVal
% objects replaced by their "foo" property.
% This could be passed into a uitable, and is used in disp()
cls = varfun( @(x)isa(x,'MyVal'), obj.table_, 'OutputFormat', 'uniform' );
num = obj.table_;
for ii = find(cls)
num.(num.Properties.VariableNames{ii}) = [num.(num.Properties.VariableNames{ii}).foo].';
end            
end
end
methods % Overloaded to emulate table behaviour        
function disp( obj )
% Overload the disp function (also called when semi colon is
% omitted) to output the numeric version of the table
disp( obj.numeric );
end
% Overload subsref and subsasgn for table indexing
function varargout = subsref( obj, s )
[varargout{1:nargout}] = builtin( 'subsref', obj.table_, s );
end
function obj = subsasgn( obj, s, varargin )
obj.table_ = builtin( 'subsasgn', obj.table_, s, varargin{:} );
end    
% Have to overload size and isa for workspace preview
function sz = size( obj, varargin )
sz = size( obj.table_, varargin{:} );
end
function b = isa( obj, varargin )
% This is only OK to do because we overloaded subsref/subsasgn
b = isa( obj.table_, varargin{:} );
end        
end
end

Answer 2

只有一半答案

我找不到自定义对象的table的显示的方法，但是如果你可以通过使用对象的arrays来获得，有一种方法，在自定义对象显示类中描述。

对于您的示例，您必须使用:matlab.mixin.CustomDisplay派生类，然后覆盖displayNonScalarObject方法:

classdef MyVal < matlab.mixin.CustomDisplay
properties
foo
end
methods
function self = MyVal(varargin)
if nargin > 0
self.foo = varargin{1};
end
end
end

methods (Access = protected)
function displayNonScalarObject(objAry)
dimStr = matlab.mixin.CustomDisplay.convertDimensionsToString(objAry);
cName = matlab.mixin.CustomDisplay.getClassNameForHeader(objAry);
headerStr = [dimStr,' ',cName,' members:'];
header = sprintf('%sn',headerStr);
disp(header)
for ix = 1:length(objAry)
o = objAry(ix);
% OPTION 1:
% For a class with a sinle property, no need to call the
% big guns, just build your own display:
disp( [num2str(ix) ': foo = ' num2str(o.foo) ] ) ;

% OR OPTION 2: (comment option1 if you use this)
% If your class had multiple properties and you want to
% display several of them, use the MATLAB built-in functions:

% create a structure with the property names you need
% displayed:
%                 propList = struct('foo',o.foo,'prop2',o.prop2,'prop3',o.prop3);
% Then let MATLAB handle the display
%                 propgrp = matlab.mixin.util.PropertyGroup(propList);
%                 matlab.mixin.CustomDisplay.displayPropertyGroups(o,propgrp);
end
end  
end
end

现在，如果你为你的类构建一个数组，显示将是这样的:

>> foo(1) = MyVal(1); foo(2) = MyVal(2);
>> foo
foo = 
1x2 MyVal members:
1: foo = 1
2: foo = 2

当然，这只是一个例子，是高度可定制的。不幸的是，我找不到一种方法来使table对象工作。