Groovy method with optional parameters

问题

I would like to write a wrapper method for a webservice, the service accepts 2 mandatory and 3 optional parameters.

To have a shorter example, I would like to get the following code working

def myMethod(pParm1='1', pParm2='2') {
    println "${pParm1}${pParm2}"
}

myMethod();
myMethod('a')
myMethod(pParm2:'a') // doesn't work as expected
myMethod('b','c')

The output is:

12
a2
[pParm2:a]2
a2
bc

What I would like to achieve is to give one parameter and get 1a as the result. Is this possible (in the laziest way)?

回答1:

Can't be done as it stands... The code

def myMethod(pParm1='1', pParm2='2'){
    println "${pParm1}${pParm2}"
}

Basically makes groovy create the following methods:

Object myMethod( pParm1, pParm2 ) {
    println "$pParm1$pParm2"
}

Object myMethod( pParm1 ) {
    this.myMethod( pParm1, '2' )
}

Object myMethod() {
    this.myMethod( '1', '2' )
}

One alternative would be to have an optional Map as the first param:

def myMethod( Map map = [:], String mandatory1, String mandatory2 ){
    println "${mandatory1} ${mandatory2} ${map.parm1 ?: '1'} ${map.parm2 ?: '2'}"
}

myMethod( 'a', 'b' )                // prints 'a b 1 2'
myMethod( 'a', 'b', parm1:'value' ) // prints 'a b value 2'
myMethod( 'a', 'b', parm2:'2nd')    // prints 'a b 1 2nd'

Obviously, documenting this so other people know what goes in the magical map and what the defaults are is left to the reader ;-)

回答2:

You can use arguments with default values.

def someMethod(def mandatory,def optional=null){}

if argument "optional" not exist, it turns to null.

来源：https://stackoverflow.com/questions/18149102/groovy-method-with-optional-parameters

标签

groovy

syntax

optional-parameters