MATLAB SIMULINK 7 - GRAPHICAL USER INTERFACE Specifikace stáhnout pdf (Strana 104)

4 Programming GUIs

4-4

•Execution Paths in the Application M-File

•Initializing the GUI

•Managing GUI Data with the Handles Structure

Execution Paths in the Application M-File

The application M-file follows different execution paths depending on what

arguments you use. For example:

•Calling the M-file with no arguments launches the GUI (if you assign an

output argument, the M-file returns the handle of the GUI figure).

•Calling the M-file with the name of a subfunction as the first argument

executes that specific subfunction (typically, but not necessarily, a callback

routine).

The Switchyard Code

The application M-file contains a “switchyard” that enables it to switch to

various execution paths depending on how it is called.

The switchyard is implemented using the

feval function. feval executes the

subfunction whose name is passed as a string argument in a call to the

application M-file.

feval executes within a try/catch statement to catch errors caused by passing

the name of nonexistent subfunctions. The following code generated by GUIDE

implements the switchyard (you should not modify this code since the

functioning of the GUI depends on its correct behavior).

if nargin == 0 % If no arguments, open GUI

fig = openfig(mfilename,'reuse');

elseif ischar(varargin{1}) % INVOKE NAMED SUBFUNCTION OR CALLBACK

try

if (nargout)

[varargout{1:nargout}] = feval(varargin{:});

else

feval(varargin{:}); % FEVAL switchyard

end

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MATLAB SIMULINK 7 - GRAPHICAL USER INTERFACE Specifikace Strana 104