Switch statement not recognizing a valid input

2 次查看（过去 30 天）
James Dossett
James Dossett 2016-2-26
评论： Jan 2016-2-28
I'm making a GUI and it has this code:
% --- Executes on selection change in AverageItem.
function AverageItem_Callback(hObject, eventdata, handles)
% hObject handle to AverageItem (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
%
% Hints: contents = cellstr(get(hObject,'String')) returns AverageItem contents as cell array
% contents{get(hObject,'Value')} returns selected item from AverageItem
% Determine the selected data set.
str = get(hObject, 'String');
val = get(hObject,'Value');
% Set current data to the selected data set.
switch str{val};
case 'Phase (Degrees)' % User selects Phase (Degrees)
AverageItem = 1;
case 'Magnitude (V/m)' % User selects Magnitude (V/m)
AverageItem = 2;
case 'RCS (dBsm)' % User selects RCS (dBsm)
AverageItem = 3;
otherwise
error(['Unknown Choice: ' str{val}])
end
% Save the data to the workspace
assignin('base','AverageItem',AverageItem);
The problem is, whenever I choose 'RCS (dBsm)' in the GUI, it does not set AverageItem = 3. It just displays the 'Unknown Choice:' error. Any ideas? Phase and Magnitude work just fine. Thanks!

请先登录，再回答此问题。

采纳的回答

Titus Edelhofer
Titus Edelhofer 2016-2-26
Hi,
it must be then that the two strings are not equal. Put a breakpoint before the switch and compare str{val} with 'RCS (dBsm)'. Sometimes it helps to convert to doubles (i.e. ascii numbers) to see the difference.
double('RCS (dBsm)')
ans =
82 67 83 32 40 100 66 115 109 41
A tab might look like one space for example.
Titus
  3 个评论
显示 1更早的评论
Jan
Jan 2016-2-28
To catch similar problems I add delimiters to the error messages:
error('Unknown Choice: [%s]', str{val})
This shows trailing spaces and does not fail in case of escape characters inside the string. The output of ['Unknown Choice: ' str] is undefined, if str contains e.g. '%s' and the output is unexpected, when control characters like \t, \n or the backspace \b are included.

请先登录，再进行评论。

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Graphics Object Programming 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