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November 10, 2009

Groovy Goodness: Define Your Own Type Conversion

In Groovy we can override the method asType() to convert an object into another type. We can use the method asType() in our code to invoke the conversion, but we can even make it shorter an use as.

class Size {
    def x, y
    
    Object asType(Class clazz) {
        if (clazz == SquaredSize) {
            new SquaredSize(x: x**2, y: y**2)
        }
    }
}

class SquaredSize {
    def x, y
    
    String toString() { "x: $x, y: $y" }
}

def size = new Size(x: 10, y: 5)
def squared = size as SquaredSize  // Or size.asType(SquaredSize)

println squared  // Output: x: 100, y: 25

assert 100 == squared.x
assert 25 == squared.y