adding a fresh .NET assembly gives a warning : Warning: Assembly xxx has already been added from location

Question

Doctor G 2017-10-23

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/362833-adding-a-fresh-net-assembly-gives-a-warning-warning-assembly-xxx-has-already-been-added-from-lo

编辑： KAE 2022-4-18

I have a very simple .m class, that has a method called setup that adds a .NET assembly, But I get a warning that the assembly is already added.

Well, there was no Matlab running. I launched a fresh copy. Setup is only called once. The line (#18) that adds the assembly (according to the debugger) is only called once. In fact, I checked to see if the assembly was added before the setup, and it returned false, i.e. that the assembly was not found.

So what gives?

(I know, this is only a warning, and the code still works, but this is frustrating).

classdef liveFeed < handle
    %eFeed Recieves live entities values (PDU data) from VR-Link
    %   DIS PDU's are captured by the C# feeder.dll from the UDP
    %   bus and translated by VR-Link code to Entity objects
    %   user should subscribe the the entities they want and will get
    %   them as messages
      properties
          asm
          feed
          result
      end
      methods
          function this = liveFeed
          end
          function setup(this)
              this.asm = NET.addAssembly(fullfile(fileparts(mfilename('fullpath')), '..\bin\MatLink.dll'));
              this.feed = linkware.Feeder('me');
              addlistener(this.feed,'NextEntity',@this.processEntry);
          end 
          function classView(this)
              methodsview(this.feed);
          end
          function fire(this)
              this.feed.fire();
          end
          function processEntry(this, ~, entry)
              this.result = char(entry.name);
              disp(this.result);
          end
          function classList(this)
              disp(this.asm.Classes);
          end
      end
  end
>> l = liveFeed
l = 
    liveFeed with properties:
         asm: []
        feed: []
      result: []
>> isempty(which('linkware.Feeder'))
ans =
    logical
     1
>> l.setup
18              this.asm = NET.addAssembly(fullfile(fileparts(mfilename('fullpath')), '..\bin\MatLink.dll'));
Warning: Assembly 'D:\CERDEC\LinkWare\bin\MatLink.dll' has already been added from location
'MatLink'. 
> In liveFeed/setup (line 18) 
>> isempty(which('linkware.Feeder'))
ans =
    logical
     0

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Doctor G 2017-10-24

编辑：Doctor G 2017-10-24

在 MATLAB Online 中打开

if true
  % code
endIs there some hidden thing in

fullfile(fileparts(mfilename('fullpath'))

that might cause the code to execute twice? since if I just hard code the path, it seems not to give this problem?

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Answer 1

Guillaume 2017-10-24

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https://ww2.mathworks.cn/matlabcentral/answers/362833-adding-a-fresh-net-assembly-gives-a-warning-warning-assembly-xxx-has-already-been-added-from-lo#answer_287561

在 MATLAB Online 中打开

I'm not really sure why your code is not working properly. However, since asm is supposed to be a singleton, defining it as a constant property would ensure that it is only evaluated once, when the class is loaded:

classdef liveFeed < handle
    %eFeed Recieves live entities values (PDU data) from VR-Link
    %   DIS PDU's are captured by the C# feeder.dll from the UDP
    %   bus and translated by VR-Link code to Entity objects
    %   user should subscribe the the entities they want and will get
    %   them as messages
        properties (Constant)
            asm = NET.addAssembly(fullfile(fileparts(mfilename('fullpath')), '..\bin\MatLink.dll'));
        end
        properties
            feed
            result
        end

The rest of your setup function can then go into the class constructor.

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Doctor G 2017-10-25

thank you that was enough to get me going on the solution.

KAE 2022-4-18

编辑：KAE 2022-4-18

@Guillaume, where in your code is asm defined as a constant? Is it the 'Constant' argument to properties? Link doesn't work but I believe it pointed here.

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