Squeak book
Ralph Johnson
johnson at cs.uiuc.edu
Fri Jan 1 20:31:52 UTC 1999
Breakpoints are not that hard to implement. Bob Hinkle did a
version a few years back for VisualWorks. You can find the
code in http://st-www.cs.uiuc.edu/ftp/pub/Smalltalk/st80_vw/Breakpoint20.st
Bob's package not only lets you put a breakpoint anywhere, it
lets you do it for a single object, so you can trap the send of add:
to one particular OrderedCollection and not have it affect any others.
There is a commercial breakpoint package that does something similar.
I assume both packages work the same. Bob's package worked by
recompiling the method with a "self halt" in it, but not changing the
source. He let you put a breakpoint on a single object by using
lightweight classes and giving an object with its own breakpoints
its own class. I am sure that the details of how to do this will be
different for Squeak, but the main idea should be the same.
-Ralph
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