Does powershell have a method_missing()?

Question

I have been playing around with the dynamic abilities of powershell and I was wondering something

Is there is anything in powershell analogous to Ruby's method_missing() where you can set up a 'catch all method' to dynamically handle calls to non-existant methods on your objects?

Answer 1

No, not really. I suspect that the next version of PowerShell will become more in line with the dynamic dispatch capabilities added to .NET 4 but for the time being, this would not be possible in pure PowerShell.

Although I do recall that there is a component model similar to that found in .NET's TypeDescriptor for creating objects that provide properties and methods dynamically to PowerShell. This is how XML elements are able to be treated like objects, for example. But this is poorly documented if at all and in my experience, a lot of the types/methods needed to integrate are marked as internal.

Answer 2

You can emulate it, but it's tricky. The technique is described in Lee Holmes book and is boiled down to two scripts - Add-RelativePathCapture http://poshcode.org/2131 and New-CommandWrapper http://poshcode.org/2197.

The essence is - you can override any cmdlet via New-CommandWrapper. Thus you can redefine Out-Default that is implicitly invoked at the end of almost every command (excluding commands with explicit formatters like Format-Table at the end). In the new Out-Default you check if the last command threw an exception saying that no method / property was found. And there you insert your method_missing logic.

Answer 3

You could use Try Catch within Powershell 2.0

http://blogs.technet.com/b/heyscriptingguy/archive/2010/03/11/hey-scripting-guy-march-11-2010.aspx