Retrieve an object's name

60 次查看（过去 30 天）
Christopher Ison
Christopher Ison 2011-7-7
评论： Steven Lord 2021-5-31
I've used Matlab a long time (10+ years) but for the life of me I can't do something rather stupidly simple: get an object's name (not its class name but the name of a specific instance). For testing purposes, I just need a function to print out the name of a specific instance of an object. Surely there is a straightforward way to do this that I'm overlooking but it doesn't easily show up in any of the help retrievals I've tried. None of my fellow Matlab users here at work could give me any help. (I know I'm going to be red-faced when I learn (relearn?) the method.)

请先登录，再回答此问题。

采纳的回答

Sean de Wolski
Sean de Wolski 2011-7-7
whos
?
x = whos;
idx = cellfun(@(x)strcmp(x,'double'),{x(:).class}); %change 'double' to your class
x(idx).name
  5 个评论
显示 3更早的评论
CCC
CCC 2021-5-31
I would like to do that with a method within the instance itself.
If you use evalin for example in 'base' you may overwrite x if exists (can be solved)
but then you get, as Lucas mentioned a list of the same class, you could add a unique property to each instance so that:
Looking for something more elegant!
function charname = getInstanceName(obj)
% Handle this variables as inputs, properties or whatever you want:
yourclass = obj.type; % Any comand that returns your instance's class.
workspaceoftheinstance = 'base';
propertyID = 'Reference'; % Any unique ID of your instance.
% Just a way to avoid using X, looking for a better one, or
% simply use the 'else'.
if ~evalin(workspaceoftheinstance,'exist(''x'')')
evalin(workspaceoftheinstance,'x = whos;');
x = evalin('base','x');
else
evalin(workspaceoftheinstance,...
'super_long_variable_name_nobody_would_use_for_this = whos;');
x = evalin(workspaceoftheinstance,...
'super_long_variable_name_nobody_would_use_for_this');
end
% Same as the Accepted Answer:
idx = cellfun(@(x)strcmp(x,yourclass),{x(:).class});
instances = x(idx);
if length(instances)>1
% We try to solve the list of instances of the same class with the
% unique .Reference property (same solution as Accepted Answer):
for i = 1:length(instances)
if evalin(workspaceoftheinstance,['strcmp(',instances(i).name,'.',propertyID,...
',''',obj.Reference,''')'])
charname = instances(i).name;
obj.varname = instances(i).name;
break
end
end
else
% There's only one.
charname = instances.name;
obj.varname = instances.name;
end
end
Steven Lord
Steven Lord 2021-5-31
Ran in:
IF you're doing this for diagnostic purposes (to include the name of the input in a warning or error message) and not to try to reach into the calling workspace to modify the object and if you're able to handle the scenario where the input has no name use inputname.
x = 1:10;
showInputName(x)
The name of the input is 'x'.
showInputName(1:10)
The input has no name.
function showInputName(in)
s = inputname(1);
if isempty(s)
fprintf("The input has no name.\n")
else
fprintf("The name of the input is '%s'.\n", s)
end
end

请先登录，再进行评论。

更多回答（2 个）

Christopher Ison
Christopher Ison 2011-7-8
Well, I found the short answer and it's really, really stupid:
function namestr = getobjname(obj)
namestr = inputname(1);
So if I type this at the command line:
namestring = getobjname(myobject)
If "myobject" exists, it returns
>>namestring = myobject
which can now be printed in an output display. Very helpful, Mathworks.
  4 个评论
显示 2更早的评论
Lucas Schneeberger
Lucas Schneeberger 2020-4-1
编辑：Lucas Schneeberger 2020-4-1
Is there a way to get the name of the instance inside the class constructor ? I would like to assign a value to obj.name property during the object construction.
This would require the left part of the assignment as in
instance_name = Class(varargin)
to be already processed when constructing the object, I am not sure if it is the case ...
Steven Lord
Steven Lord 2020-4-1
I would like to assign a value to obj.name property during the object construction.
See the "Initializing Objects in Constructor" section on this documentation page for several examples of how to do this. There's no need to know with what name the class constructor was called to store the output (or even if that output has a name: mycell{1} = myObjectConstructor; is a perfectly valid way to call an object constructor and store the resulting object in a cell in a cell array.)

请先登录，再进行评论。

Paul O'Brien
Paul O'Brien 2018-11-13
In MatLab R2016b, if I have a variable "obj" referring to an object, you can get a list of methods by typing
obj.
and then pressing the tab key. One of the methods is called "string", and
obj.string
yields a string containing the name of the object.
  1 个评论
Steven Lord
Steven Lord 2018-11-13
That assumes that the class author has chosen to overload the string method to behave that way. As an example of where this could fail is the table class:
>> t = array2table(magic(4));
>> class(t)
ans =
'table'
>> string(t)
Error using string
Conversion to string from table is not possible.
This is one case where string(t) and t.string behave differently, but neither gives the name of the variable.
>> t.string
Unrecognized variable name 'string'.

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Entering Commands 的更多信息

标签

产品

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by