classdef (Abstract) FileExtractor < handle
% Extract the variables defined in a .txt file.
%
% Example:
%   given an example.txt file wich contains only one line:
%
%     foo = 42
%
%   running:
%
%     test = FileExtractor.getVariableFromTextFile('foo','example.txt');
%
%   will attribute the value 42 to the variable 'test'. The same result
%   that would have been given by running:
% 
%     test = 42; 

  properties (Abstract, Constant)
    filename
  end



  methods (Static)

    function output = getVariableFromTextFile(variableName,filename)
      output = [];
      assert(ischar(filename),'filename must be a char array')
      assert(ischar(variableName),'variableName must be a char array')
      assert( (exist(filename,'file') == 2),'File %s doesn''t exist',filename);
      fid = fopen(filename,'r');
      while and(isempty(output), not(feof(fid)))
        line = fgetl(fid);
        variableFound = extractAfter(line,[variableName ' = ']);
        if not(isempty(variableFound))
          eval(['output = ' variableFound ';']);
        end
      end
      assert(not(isempty(output)),'%s has not been found in %s',variableName,filename);
      fclose(fid);
    end

  end


end