User ending a program

[ktkoh]

I have used "exit" in my joint tool program for cases where the user's selection was in error or when a data form asked for input that the user did not have so they selected cancel. I do see that this produces an error message in the ruby console so I am asking if this is unacceptable practice? I found that if the space bar is pressed the selection tool is activated and my tool dropped but Sketchup.send_action "selectSelectionTool:" does not do anything.

Keith

[Dan Rathbun]

@ktkoh said:

I have used "exit" in my joint tool program ...

Is this an external script running in a system Ruby process, or a SketchUp extension running in an embedded Ruby subprocess ?

Raising a SystemExit exception has only good use in a system Ruby script, and no good use in an embedded Ruby subprocess.

So, yes, within SketchUp, it is poor practice. It is better to raise a RuntimeError exception with a custom message, or create your own exception subclasses within your extension namespace.

Here is a simple example:
Custom_Exception_SubClasses.rb

# encoding ; UTF-8

# A simple example of creating your own Exception
#  sub-classes inside your own namespace modules.
#
# fail() is an alias for raise(), and most coding style guides
# prefer that fail() is used when first causing an exception,
# and raise() is used when re-raising a current exception within
# a rescue block.

module Author # <--<<< Change to unique toplevel namespace module.

  module SomeParticularPlugin

    VERSION = '1.0.0'
    
    InputCancellation = Class.new(RuntimeError)
    InvalidSelection  = Class.new(RuntimeError)
    NoGroupsSelected  = Class.new(RuntimeError)

    # In this module we assume that the module variables; @@prompts,
    #  @@defaults, @@choices & @@caption have already been defined.

    def get_input(selection_set)
      
      # First, make a decision about the selection set;
      if selection_set.empty?
        fail(InvalidSelection,"selection is empty!")
      elsif !selection_set.single_object?
        fail(InvalidSelection,"selection not single object!")
      else
        grps = selection_set.grep(Sketchup;;Group)
        if grps.empty?
          fail(NoGroupsSelected,"no groups are selected!")
        end
      end

      data = inputbox(@@prompts,@@defaults,@@choices,@@caption)
      # false if the user cancels
      fail(InputCancellation,"user cancelled") if !data
      # otherwise data is an array of values

    rescue InputCancellation => err
      UI.messagebox("Stop; #{err.message}")
      return nil
    rescue InvalidSelection => err
      UI.messagebox("Selection Error; #{err.message}")
      return false
    rescue => err # any other exception
      # recover gracefully
      UI.messagebox("Error; #{err.message}")
      return false
    else # no errors
      # code to execute when input is valid
      return data
    end ###

  end # specific plugin module
end # outermost namespace module

[ktkoh]

Thanks Dan that really helped me. I had never run across the term fail() and was able to research this in the ruby help files I use. I have tested it in my program and find it works as you described.

Keith

[Dan Rathbun]

@ktkoh said:

Thanks Dan that really helped me.

Cool! That was the purpose.

@ktkoh said:

I had never run across the term fail() and was able to research this in the ruby help files I use.

Kerenl#fail() is just an alias for Kernel#raise().
(I explained this in the file comments, and why I use it, instead of raise.)

@ktkoh said:

I have tested it in my program and find it works as you described.

I just noticed an error, although the example should still work.

Line 38 was meant to be:
data = UI.inputbox(@@prompts,@@defaults,@@choices,@@caption)

Currently it is:
data = inputbox(@@prompts,@@defaults,@@choices,@@caption)
which uses the global inputbox() retry wrapper method defined in " %(black)[Tools/sketchup.rb]". So then the " %(black)[sketchup.rb]" file must be loaded first.

If y'all prefer, you can call the UI.inputbox() module method directly and bypass the retry wrapper.

[Dan Rathbun]

So, you realize that although you could handle this scenario with very long cluttered if ... elsif ... else constructs, likely with a bunch of nested if statements,... that would be hard to maintain and use more lines.

This way condenses the code, and makes it more readable, and easier to maintain.

[ktkoh]

The program I used as a model when starting used that method. However as I added more functions it became almost impossible to find how to get out to the end of the mouse click down def.

Keith