Create dynamically closures in Groovy from a String object - grails

Question

i would like to create a query with the Criteria API in Grails (GORM).
The query will have to be something like this:
MyEntity.createCriteria().list{
assoc{
parent{
eq("code", val)
}
}
}
What i need is to build the nested closure dynamically from a String object. The String for the example above will be "assoc.parent.code" . I splitted the String by dot (by doing String.split("\\.") ) but i don't know how to construct the nested closures:
assoc{
parent{
eq("code", val)
}
}
dynamically based on the array of the splitted Strings above.

Answer 1

What about createAlias?. You could try something like this:
def path = "assoc.parent.code"
def split = path.split(/\./)
MyEntity.createCriteria().list {
// this will get you 'createAlias( assoc.parent, alias1 )'
createAlias split.take( split.size() - 1 ), "alias1"
// this will get you 'eq(alias1.code, userInput)'
eq "alias1.${split[-1]}", userInput
}
This snippet is not generic, but you get the idea.
Update
Not conventional, but you can build a string containing the code with the closures and evaluate it using GroovyShell:
assoc = 'assoc.parent.child.name'
split = assoc.split( /\./ )
path = split[-2..0] // will get us 'child.parent.assoc';
// we will build it from inside-out
def firstClosure = "{ eq '${split[-1]}', 'john doe' }"
def lastClosure = firstClosure
for (entity in path) {
def criteriaClosure = "{ ${entity} ${lastClosure} }"
lastClosure = criteriaClosure
}
assert lastClosure == "{ assoc { parent { child { eq 'name', 'john doe' } } } }"
def builtClosure = new GroovyShell().evaluate("return " + lastClosure)
assert builtClosure instanceof Closure

Answer 2

A more generic approach would be to metaClass String as below, and use it for any kind of separator
. | , - ~ and more.
String.metaClass.convertToClosureWithValue = {op, val ->
split = delegate.split(op) as List
if(split.size() == 1) {return "Cannot split string '$delegate' on '$op'"}
items = []
split.each{
if(it == split.last()){
items << "{ eq '$it', $val }"
split.indexOf(it).times{items.push("}")}
} else {
items << "{$it"
}
}
println items.join()
new GroovyShell().evaluate("return " + items.join())
}
assert "assoc.parent.child.name".convertToClosureWithValue(/\./, "John Doe") instanceof Closure
assert "assoc-parent-child-name".convertToClosureWithValue(/\-/, "Billy Bob") instanceof Closure
assert "assoc|parent|child|grandChild|name".convertToClosureWithValue(/\|/, "Max Payne") instanceof Closure
assert "assoc~parent~child~grandChild~name".convertToClosureWithValue('\\~', "Private Ryan") instanceof Closure
assert "assocparentchildname".convertToClosureWithValue(/\|/, "Captain Miller") == "Cannot split string 'assocparentchildname' on '\\|'"
//Print lines from items.join()
{assoc{parent{child{ eq 'name', John Doe }}}}
{assoc{parent{child{ eq 'name', Billy Bob }}}}
{assoc{parent{child{grandChild{ eq 'name', Max Payne }}}}}
{assoc{parent{child{grandChild{ eq 'name', Private Ryan }}}}}