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Matlab enums matlab-class

如何在 MATLAB 中创建枚举类型？

发布于 2024-08-04 05:57:21 字数 36 浏览 6 评论 0 原文

MATLAB 中有枚举类型吗？如果没有，还有哪些替代方案？

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热鲨 2024-08-11 05:57:21

从 R2010b 开始，MATLAB 支持枚举。

文档中的示例：

classdef Colors
   properties
      R = 0;
      G = 0;
      B = 0;
   end

   methods
      function c = Colors(r, g, b)
         c.R = r; c.G = g; c.B = b;
      end
   end

   enumeration
      Red   (1, 0, 0)
      Green (0, 1, 0)
      Blue  (0, 0, 1)
   end
end

Starting from R2010b, MATLAB supports enumerations.

Example from the documentation:

classdef Colors
   properties
      R = 0;
      G = 0;
      B = 0;
   end

   methods
      function c = Colors(r, g, b)
         c.R = r; c.G = g; c.B = b;
      end
   end

   enumeration
      Red   (1, 0, 0)
      Green (0, 1, 0)
      Blue  (0, 0, 1)
   end
end

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花心好男孩 2024-08-11 05:57:21

您可以使用新型 MATLAB 类获得一些功能：

classdef (Sealed) Colors
    properties (Constant)
        RED = 1;
        GREEN = 2;
        BLUE = 3;
    end

    methods (Access = private)    % private so that you cant instantiate
        function out = Colors
        end
    end
end

这并不是真正的类型，但由于 MATLAB 是松散类型的，如果您使用整数，您可以执行近似它的操作：

line1 = Colors.RED;
...
if Colors.BLUE == line1
end

在本例中，MATLAB“枚举”接近 C 风格的枚举 - 整数的替代语法。

通过仔细使用静态方法，您甚至可以使 MATLAB 枚举在复杂性上接近 Ada，但不幸的是语法更加笨拙。

You can get some of the functionality with new-style MATLAB classes:

classdef (Sealed) Colors
    properties (Constant)
        RED = 1;
        GREEN = 2;
        BLUE = 3;
    end

    methods (Access = private)    % private so that you cant instantiate
        function out = Colors
        end
    end
end

This isn't really a type, but since MATLAB is loosely typed, if you use integers, you can do things that approximate it:

line1 = Colors.RED;
...
if Colors.BLUE == line1
end

In this case, MATLAB "enums" are close to C-style enums - substitute syntax for integers.

With the careful use of static methods, you can even make MATLAB enums approach Ada's in sophistication, but unfortunately with clumsier syntax.

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暖心男生 2024-08-11 05:57:21

如果您想做一些类似于 Marc 建议的事情，您只需制作一个结构来表示您的枚举类型而不是一个全新的类：

colors = struct('RED', 1, 'GREEN', 2, 'BLUE', 3);

一个好处是您可以通过两种不同的方式轻松访问结构。您可以直接使用字段名称指定字段：

a = colors.RED;

或者可以使用动态字段名称（如果您在字符串中包含字段名称）：

a = colors.('RED');

事实上，按照 Marc 建议并创建一个全新的类来表示“枚举”对象有一些好处

：可以控制对象的修改方式。
您可以将定义保留在一处，并轻松地在多个地方使用它。
您可以控制失败并使它们更加“优雅”，例如如果您尝试访问不存在的字段，则返回一个空矩阵（而不是抛出错误）。

但是，如果您不需要这种复杂性而只需要快速执行某些操作，那么结构可能是最简单、最直接的实现。它还可以与不使用最新 OOP 框架的旧版本 MATLAB 配合使用。

If you want to do something similar to what Marc suggested, you could simply make a structure to represent your enumerated types instead of a whole new class:

colors = struct('RED', 1, 'GREEN', 2, 'BLUE', 3);

One benefit is that you can easily access structures in two different ways. You can specify a field directly using the field name:

a = colors.RED;

or you can use dynamic field names if you have the field name in a string:

a = colors.('RED');

In truth, there are a few benefits to doing what Marc suggested and creating a whole new class to represent an "enum" object:

You can control how the object is modified.
You can keep the definition in one place and easily use it in multiple places.
You can control failures and make them more "graceful", like returning an empty matrix if you try to access a non-existent field (as opposed to throwing an error).

However, if you don't need that sort of complexity and just need to do something quick, a structure is likely the easiest and most straight-forward implementation. It will also work with older versions of MATLAB that don't use the newest OOP framework.

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怼怹恏 2024-08-11 05:57:21

您还可以使用 Matlab 代码中的 Java 枚举类。在 Java 中定义它们并将它们放在 Matlab 的 javaclasspath 中。

// Java class definition
package test;
public enum ColorEnum {
    RED, GREEN, BLUE
}

您可以在 M 代码中通过名称引用它们。

mycolor = test.ColorEnum.RED
if mycolor == test.ColorEnum.RED
    disp('got red');
else
    disp('got other color');
end

% Use ordinal() to get a primitive you can use in a switch statement
switch mycolor.ordinal
    case test.ColorEnum.BLUE.ordinal
        disp('blue');
    otherwise
        disp(sprintf('other color: %s', char(mycolor.toString())))
end

但它不会与其他类型进行比较。与字符串的比较有一个奇怪的返回大小。

>> test.ColorEnum.RED == 'GREEN'
ans =
     0
>> test.ColorEnum.RED == 'RED'
ans =
     1     1     1

You could also use Java enum classes from your Matlab code. Define them in Java and put them on your Matlab's javaclasspath.

// Java class definition
package test;
public enum ColorEnum {
    RED, GREEN, BLUE
}

You can reference them by name in M-code.

mycolor = test.ColorEnum.RED
if mycolor == test.ColorEnum.RED
    disp('got red');
else
    disp('got other color');
end

% Use ordinal() to get a primitive you can use in a switch statement
switch mycolor.ordinal
    case test.ColorEnum.BLUE.ordinal
        disp('blue');
    otherwise
        disp(sprintf('other color: %s', char(mycolor.toString())))
end

It won't catch comparisons to other types, though. And comparison to string has an odd return size.

>> test.ColorEnum.RED == 'GREEN'
ans =
     0
>> test.ColorEnum.RED == 'RED'
ans =
     1     1     1

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淡紫姑娘！ 2024-08-11 05:57:21

MATLAB R2009b 中实际上有一个名为'enumeration' 的关键字。它似乎没有记录，我不能说我知道如何使用它，但功能可能是存在的。

您可以在 matlabroot\toolbox\distcomp\examples\+examples 中找到它

classdef(Enumeration) DmatFileMode < int32

    enumeration
        ReadMode(0)
        ReadCompatibilityMode(1)
        WriteMode(2)
    end
<snip>
end

There is actually a keyword in MATLAB R2009b called 'enumeration'. It seems to be undocumented, and I cannot say I know how to use it, but the functionality is probably there.

You can find it in matlabroot\toolbox\distcomp\examples\+examples

classdef(Enumeration) DmatFileMode < int32

    enumeration
        ReadMode(0)
        ReadCompatibilityMode(1)
        WriteMode(2)
    end
<snip>
end

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莫相离 2024-08-11 05:57:21

你可以创建一个Matlab类，其行为类似于Java的旧类类型安全枚举模式。对Marc的解决方案进行修改可以接受它从 C 风格的 typedef 到更像 Java 风格的类型安全枚举。在此版本中，常量中的值是类型化的 Color 对象。

优点：

可以通过 == 和其他操作检查类型（在运行时），以防止与原始数字或其他类型的枚举的意外比较。
您可以显式检查变量的类型（在运行时）。
值以可读名称显示，而不是不透明的代码。
不允许像mean() 和std() 这样对枚举没有意义的操作。

缺点：

类定义较长。但是，这都是样板文件，可以重用于任何其他枚举类，只需更改类名和常量属性。
这些枚举不能直接在 switch 块中使用。需要弹出代码，这会失去一些类型安全性。
对象会比基元慢。如果您在循环内使用常量，则相关。

总的来说，我不知道哪种方法更好。实践中也没用过。

classdef (Sealed) Color
%COLOR Example of Java-style typesafe enum for Matlab

properties (Constant)
    RED = Color(1, 'RED');
    GREEN = Color(2, 'GREEN');
    BLUE = Color(3, 'BLUE');
end
properties (SetAccess=private)
    % All these properties are immutable.
    Code;
    Name;
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
methods (Access = private)
%private so that you can't instatiate directly
    function out = Color(InCode, InName)
        out.Code = InCode;
        out.Name = InName;
    end       
end
methods (Static = true)
    function needa(obj)
    %NEEDA Asserts that obj must be a Color
        if ~isa(obj, mfilename)
            error('Input must be a %s; got a %s', mfilename, class(obj));
        end
    end
end
methods (Access = public)
    function display(obj)
      disp([inputname(1) ' =']);
      disp(obj);
    end
    function disp(obj)
        if isscalar(obj)
            disp(sprintf('%s: %s (%d)', class(obj), obj.Name, obj.Code));
        else
            disp(sprintf('%s array: size %s', class(obj), mat2str(size(obj))));
        end
    end    
    function out = eq(a, b)
        %EQ Basic "type-safe" eq
        check_type_safety(a, b);
        out = [a.Code] == [b.Code];
    end
    function [tf,loc] = ismember(a, b)
        check_type_safety(a, b);
        [tf,loc] = ismember([a.Code], [b.Code]);
    end
    function check_type_safety(varargin)
        %CHECK_TYPE_SAFETY Check that all inputs are of this enum type
        for i = 1:nargin
            if ~isa(varargin{i}, mfilename)
                error('Non-typesafe comparison of %s vs. %s', mfilename, class(varargin{i}));
            end
        end
    end
end
end

这是一个练习它的函数。

function do_stuff_with_color(c)
%DO_STUFF_WITH_COLOR Demo use of the Color typesafe enum

Color.needa(c); % Make sure input was a color
if (c == Color.BLUE)
    disp('color was blue');
else
    disp('color was not blue');
end

% To work with switch statements, you have to explicitly pop the code out 
switch c.Code
    case Color.BLUE.Code
        disp('blue');
    otherwise
        disp(sprintf('some other color: %s', c.Name));
end

使用示例：

>> Color.RED == Color.RED
ans =
     1
>> Color.RED == 1
??? Error using ==> Color>Color.check_type_safety at 55
Non-typesafe comparison of Color vs. double

Error in ==> Color>Color.eq at 44
        check_type_safety(a, b);

>> do_stuff_with_color(Color.BLUE)
color was blue
blue
>> do_stuff_with_color(Color.GREEN)
color was not blue
some other color: GREEN
>> do_stuff_with_color(1+1) % oops - passing the wrong type, should error
??? Error using ==> Color>Color.needa at 26
Input must be a Color; got a double

Error in ==> do_stuff_with_color at 4
Color.needa(c); % Make sure input was a color

>>

这两种方法都有一个小问题：将常量放在“==”左侧以防止错误赋值的 C 约定在这里没有多大帮助。在 Matlab 中，如果您不小心在 LHS 上使用“=”与此常量，它只会创建一个名为 Colors 的新局部结构变量，而不是出现错误，并且会屏蔽枚举类。

>> Colors.BLUE = 42
Colors = 
    BLUE: 42
>> Color.BLUE = 42
Color = 
    BLUE: 42
>> Color.RED
??? Reference to non-existent field 'RED'.

You could make a Matlab class that behaves like a Java's old typesafe enum pattern. A modification of Marc's solution could take it from C-style typedefs to more like Java-style typesafe enums. In this version, the values in the constants are typed Color objects.

The upsides:

The type can be checked (at runtime) by == and other operations to prevent accidental comparison to raw numerics or other types of enums.
You can explicitly check the type of your variables (at runtime).
Values are displayed with readable names instead of the opaque codes.
Operations like mean() and std() that don't make sense on enums are disallowed.

Downsides:

Longer class definition. But, this is all boilerplate, and can be reused for any other enum class, changing just the class name and Constant properties.
These enums cannot be used directly in switch blocks. Need to pop the Code out, which loses some type safety.
Objects will be slower than primitives. Relevant if you're using constants inside loops.

On the whole, I don't know which approach is better. Haven't used either in practice.

classdef (Sealed) Color
%COLOR Example of Java-style typesafe enum for Matlab

properties (Constant)
    RED = Color(1, 'RED');
    GREEN = Color(2, 'GREEN');
    BLUE = Color(3, 'BLUE');
end
properties (SetAccess=private)
    % All these properties are immutable.
    Code;
    Name;
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
methods (Access = private)
%private so that you can't instatiate directly
    function out = Color(InCode, InName)
        out.Code = InCode;
        out.Name = InName;
    end       
end
methods (Static = true)
    function needa(obj)
    %NEEDA Asserts that obj must be a Color
        if ~isa(obj, mfilename)
            error('Input must be a %s; got a %s', mfilename, class(obj));
        end
    end
end
methods (Access = public)
    function display(obj)
      disp([inputname(1) ' =']);
      disp(obj);
    end
    function disp(obj)
        if isscalar(obj)
            disp(sprintf('%s: %s (%d)', class(obj), obj.Name, obj.Code));
        else
            disp(sprintf('%s array: size %s', class(obj), mat2str(size(obj))));
        end
    end    
    function out = eq(a, b)
        %EQ Basic "type-safe" eq
        check_type_safety(a, b);
        out = [a.Code] == [b.Code];
    end
    function [tf,loc] = ismember(a, b)
        check_type_safety(a, b);
        [tf,loc] = ismember([a.Code], [b.Code]);
    end
    function check_type_safety(varargin)
        %CHECK_TYPE_SAFETY Check that all inputs are of this enum type
        for i = 1:nargin
            if ~isa(varargin{i}, mfilename)
                error('Non-typesafe comparison of %s vs. %s', mfilename, class(varargin{i}));
            end
        end
    end
end
end

Here's a function to exercise it.

function do_stuff_with_color(c)
%DO_STUFF_WITH_COLOR Demo use of the Color typesafe enum

Color.needa(c); % Make sure input was a color
if (c == Color.BLUE)
    disp('color was blue');
else
    disp('color was not blue');
end

% To work with switch statements, you have to explicitly pop the code out 
switch c.Code
    case Color.BLUE.Code
        disp('blue');
    otherwise
        disp(sprintf('some other color: %s', c.Name));
end

Example of use:

>> Color.RED == Color.RED
ans =
     1
>> Color.RED == 1
??? Error using ==> Color>Color.check_type_safety at 55
Non-typesafe comparison of Color vs. double

Error in ==> Color>Color.eq at 44
        check_type_safety(a, b);

>> do_stuff_with_color(Color.BLUE)
color was blue
blue
>> do_stuff_with_color(Color.GREEN)
color was not blue
some other color: GREEN
>> do_stuff_with_color(1+1) % oops - passing the wrong type, should error
??? Error using ==> Color>Color.needa at 26
Input must be a Color; got a double

Error in ==> do_stuff_with_color at 4
Color.needa(c); % Make sure input was a color

>>

A minor quirk in both approaches: the C convention of putting the constant on the left hand of the "==" to prevent bad assignment doesn't help as much here. In Matlab, if you accidentally use "=" with this constant on the LHS, instead of an error, it'll just create a new local struct variable named Colors, and it will mask the enum class.

>> Colors.BLUE = 42
Colors = 
    BLUE: 42
>> Color.BLUE = 42
Color = 
    BLUE: 42
>> Color.RED
??? Reference to non-existent field 'RED'.

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初心 2024-08-11 05:57:21

如果您有权访问统计工具箱，则可以考虑使用分类对象。

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傲鸠 2024-08-11 05:57:21

在尝试了本页上的其他建议后，我采用了 Andrew 的完全面向对象的方法。非常好 - 谢谢安德鲁。

不过，如果有人感兴趣，我做了（我认为是）一些改进。特别是，我不再需要双重指定枚举对象的名称。现在使用反射和元类系统派生名称。此外，重写了 eq() 和 ismember() 函数，以返回枚举对象矩阵的正确形状的返回值。最后，修改了 check_type_safety() 函数以使其与包目录（例如命名空间）兼容。

看起来效果很好，但请告诉我你的想法：

classdef (Sealed) Color
%COLOR Example of Java-style typesafe enum for Matlab

properties (Constant)
    RED = Color(1);
    GREEN = Color(2);
    BLUE = Color(3);
end
methods (Access = private) % private so that you can''t instatiate directly
    function out = Color(InCode)
        out.Code = InCode;
    end       
end


% ============================================================================
% Everything from here down is completely boilerplate - no need to change anything.
% ============================================================================
properties (SetAccess=private) % All these properties are immutable.
    Code;
end
properties (Dependent, SetAccess=private)
    Name;
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
methods
    function out = eq(a, b) %EQ Basic "type-safe" eq
        check_type_safety(a, b);
        out = reshape([a.Code],size(a)) == reshape([b.Code],size(b));
    end
    function [tf,loc] = ismember(a, b)
        check_type_safety(a, b);
        [tf,loc] = ismember(reshape([a.Code],size(a)), [b.Code]);
    end
    function check_type_safety(varargin) %CHECK_TYPE_SAFETY Check that all inputs are of this enum type
        theClass = class(varargin{1});
        for ii = 2:nargin
            if ~isa(varargin{ii}, theClass)
                error('Non-typesafe comparison of %s vs. %s', theClass, class(varargin{ii}));
            end
        end
    end

    % Display stuff:
    function display(obj)
        disp([inputname(1) ' =']);
        disp(obj);
    end
    function disp(obj)
        if isscalar(obj)
            fprintf('%s: %s (%d)\n', class(obj), obj.Name, obj.Code);
        else
            fprintf('%s array: size %s\n', class(obj), mat2str(size(obj)));
        end
    end    
    function name=get.Name(obj)
        mc=metaclass(obj);
        mp=mc.Properties;
        for ii=1:length(mp)
            if (mp{ii}.Constant && isequal(obj.(mp{ii}.Name).Code,obj.Code))
                name = mp{ii}.Name;
                return;
            end;
        end;
        error('Unable to find a %s value of %d',class(obj),obj.Code);
    end;
end
end

谢谢，
石匠

After trying out the other suggestions on this page, I landed on Andrew's fully object-oriented approach. Very nice - thanks Andrew.

In case anyone is interested, however, I made (what I think are) some improvements. In particular, I removed the need to double-specify the name of the enum object. The names are now derived using reflection and the metaclass system. Further, the eq() and ismember() functions were re-written to give back properly-shaped return values for matrices of enum objects. And finally, the check_type_safety() function was modified to make it compatible with package directories (e.g. namespaces).

Seems to work nicely, but let me know what you think:

classdef (Sealed) Color
%COLOR Example of Java-style typesafe enum for Matlab

properties (Constant)
    RED = Color(1);
    GREEN = Color(2);
    BLUE = Color(3);
end
methods (Access = private) % private so that you can''t instatiate directly
    function out = Color(InCode)
        out.Code = InCode;
    end       
end


% ============================================================================
% Everything from here down is completely boilerplate - no need to change anything.
% ============================================================================
properties (SetAccess=private) % All these properties are immutable.
    Code;
end
properties (Dependent, SetAccess=private)
    Name;
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
methods
    function out = eq(a, b) %EQ Basic "type-safe" eq
        check_type_safety(a, b);
        out = reshape([a.Code],size(a)) == reshape([b.Code],size(b));
    end
    function [tf,loc] = ismember(a, b)
        check_type_safety(a, b);
        [tf,loc] = ismember(reshape([a.Code],size(a)), [b.Code]);
    end
    function check_type_safety(varargin) %CHECK_TYPE_SAFETY Check that all inputs are of this enum type
        theClass = class(varargin{1});
        for ii = 2:nargin
            if ~isa(varargin{ii}, theClass)
                error('Non-typesafe comparison of %s vs. %s', theClass, class(varargin{ii}));
            end
        end
    end

    % Display stuff:
    function display(obj)
        disp([inputname(1) ' =']);
        disp(obj);
    end
    function disp(obj)
        if isscalar(obj)
            fprintf('%s: %s (%d)\n', class(obj), obj.Name, obj.Code);
        else
            fprintf('%s array: size %s\n', class(obj), mat2str(size(obj)));
        end
    end    
    function name=get.Name(obj)
        mc=metaclass(obj);
        mp=mc.Properties;
        for ii=1:length(mp)
            if (mp{ii}.Constant && isequal(obj.(mp{ii}.Name).Code,obj.Code))
                name = mp{ii}.Name;
                return;
            end;
        end;
        error('Unable to find a %s value of %d',class(obj),obj.Code);
    end;
end
end

Thanks,
Mason

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醉梦枕江山 2024-08-11 05:57:21

Toys = {'Buzz', 'Woody', 'Rex', 'Hamm'};

Toys{3}
  ans = 'Rex'

Toys = {'Buzz', 'Woody', 'Rex', 'Hamm'};

Toys{3}
  ans = 'Rex'

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我不吻晚风 2024-08-11 05:57:21

如果您需要枚举类型只是为了传递给 C# 或 .NET 程序集，
您可以使用 MATLAB 2010 构造并传递枚举：

A = NET.addAssembly(MyName.dll)
% suppose you have enum called "MyAlerts" in your assembly
myvar = MyName.MyAlerts.('value_1');

您还可以查看官方 MathWorks 答案：

如何在 MATLAB 7.8 (R2009a) 中使用 .NET 枚举值？

// the enum "MyAlerts" in c# will look something like this
public enum MyAlerts
{
    value_1 = 0,
    value_2 = 1,
    MyAlerts_Count = 2,
}

If you need the enumerated types just for passing to C# or .NET assembly,
you can construct and pass the enums with MATLAB 2010:

A = NET.addAssembly(MyName.dll)
% suppose you have enum called "MyAlerts" in your assembly
myvar = MyName.MyAlerts.('value_1');

you can also check the official MathWorks answer at

How do I use .NET enumerated values in MATLAB 7.8 (R2009a)?

// the enum "MyAlerts" in c# will look something like this
public enum MyAlerts
{
    value_1 = 0,
    value_2 = 1,
    MyAlerts_Count = 2,
}

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如何在 MATLAB 中创建枚举类型？

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如何在 MATLAB 中创建枚举类型？

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