I wrote a simple UserDefinedCommand called TradeAll and a UserDefinedScript that uses it. I noticed that the exec() methods in other people's UDCs were calling initInstance() and execInstance() instead of initCommand() and startCommand(), so I copied this without understanding it.

But when I ran it, SWATH 1.9.8 hung on executing the UDC. (It said "cmd: TradeAll" in the status bar.) I added some trace messages and discovered that my command was getting executed, but it hung after returning from the startCommand() method.

When I call initCommand() and startCommand() myself, it works.

Can anyone explain what's going on? Why do people call initInstance() and execInstance()?