Is there any way to leverage Groovy's collect method in combination with another iterator function?

Question

For example, the groovy File class has a nice iterator that will filter out just directories and not files:

void eachDir(Closure closure) 

Answer 1

I don't know of any "idiomatic" way of doing this, nice riddle! =D

You can try passing the eachDir, or any similar function, to a function that will collect its iterations:

def collectIterations(fn) {
    def col = []
    fn {
        col << it
    }
    col
}

And now you can use it as:

def dir = new File('/path/to/some/dir')
def subDirs = collectIterations(dir.&eachDir)

def file = new File('/path/to/some/file')
def lines = collectIterations(file.&eachLine) 

(that last example is equivalent to file.readLines())

And only for bonus points, you may define this function as a method in the Closure class:

Closure.metaClass.collectIterations = {->
    def col = []
    delegate.call {
        col << it
    }
    col
}

def dir = new File('/path/to/some/dir')
def subDirs = dir.&eachDir.collectIterations()

def file = new File('/path/to/some/file')
def lines = file.&eachLine.collectIterations()

Update: On the other hand, you might also do:

def col = []    
someDir.eachDir col.&add

Which I think is quite less convoluted, but it's not leveraging the collect method as you requested :)