User's Guide

Adding the message halt

To interrupt the running of your code, find a place in your code where you want to gather information. Then, specify a breakpoint by adding the message halt or the expression self halt.

For example, evaluate the following code in a Workspace with the Execute command:

(OrderedCollection new)
  halt;
  add: 'Alix';
  add: 'Sam';
  add: 4;
  add: (Date today);
  at: 4 put: 'Cathy';
  yourself.

A debugger opens, showing the error message '(ExHalt) A halt has occurred.' The top of the stack has the following messages:

[] in <optimized block>(ExceptionalEvent class)>>#initializeSystemExceptions
Signal>>#evaluate:
ExceptionalEvent>>#applyDefaultHandler:
ExceptionalEvent>>#signalWithArguments:
ExceptionalEvent>>#signal
OrderedCollection(Object)>>#halt
UndefinedObject>>#Doit

Select OrderedCollection(Object)>>#halt in the message stack and inspect self in the list of variables. Notice that the ordered collection exists but contains no entries.


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