CODEWITHSUNDEEP
groovydsl
WeSt
WeSt

Reputation: 2684

Groovy - Type Check Closure Code Before Execution

I have a Groovy script that lets the user define some dynamic properties and methods and later executes a user-defined closure. A script would look like this:

// init properties and methods dynamically at runtime
context.prop1 = "Some test value"
context.method1 = { String input ->
    "exec " + input.toUpperCase()
}

// "this" is set to the context variable from above
run {
    println method1( prop1 )
}

So in the beginning of the script, a context is initialized with user-defined properties (e.g. prop1) and methods (e.g. method1). The context is then used as this pointer in the run closure. I have achieved this by dynamically extending the meta class of the context and setting the context as delegate of the run closure (with DELEGATE_FIRST as resolves strategy).

Currently I am struggling at type checking. Before executing the run closure, I would like to check if method1 really expects prop1. I have looked into the DelegatesTo annotation, but that doesn't seem to work for dynamically extended objects. I have also played with the AST, but since my knowledge on that topic is limited, I haven't come up with a solution. If what I want to achieve is possible, any pointers in the right direction would be greatly appreciated.

Upvotes: 0

Views: 512

Answers (1)

blackdrag
blackdrag

Reputation: 6518

You want to add a method to a context at runtime and then type check this before execution of that method.

Type checking is done at compile time. That is before anything of your program is executed. There is normally no chance this can ever check anything that will only happen at runtime, unless you have a way to statically declare it and give the compiler the power to do the check. But this means normally, you will have to do static compilation.

One way would be to use type checking extensions, but I think in your case that might be overkill. A more simple way would be to use extension modules. And the most simple way would be to use custom script base class.

But for any of these solution you will need static compilation to really have type checking, same for DelegatesTo (which is more used in combination with extension modules). For a type checked DSL a mix of type checking extensions and extension modules can work very well. But you will of course loose more dynamic features of the language and some simplicity.

Upvotes: 1

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