在groovy中使用默认值命名的参数

Question

是否可以在groovy中使用默认值命名参数？我的计划是创建一种对象工厂,可以在没有参数的情况下调用它,以获得具有默认值的对象.此外,我需要功能来明确设置对象的任何参数.我相信这可以通过Python关键字参数来实现.

我现在正在尝试的代码如下所示

// Factory method
def createFoo( name='John Doe', age=51, address='High Street 11') {
  return new Foo( name, age, address )
}

// Calls
Foo foo1 = createFoo()  // Create Foo with default values
Foo foo2 = createFoo( age:21 )  // Create Foo where age param differs from defaut
Foo foo3 = createFoo( name:'Jane', address:'Low Street 11' )  // You get the picture
// + any other combination available

我正在开发的真正应用程序将拥有更多参数,因此需要更多组合.

谢谢

更新:

我计划的工厂方法是用于测试目的.无法真正触及实际的Foo类,尤其不是它的默认值.

下面的@dmahapatro和@codelarks在使用Map作为参数时有一个很好的观点,它让我了解了一个可能的解决方案.我可以使用所需的默认值创建一个地图并覆盖所需的值,并将其传递给工厂方法.这可能会完成这项工作,我将继续这样做,除非我得到一个更好的方法.

我现在的方法如下

defaults = [ name:'john', age:61, address:'High Street']

@ToString(includeFields = true, includeNames = true)
class Foo {
  // Can't touch this :)
  def name = ''
  def age = 0
  def address = ''
}

def createFoo( Map params ) {
  return new Foo( params )
}

println createFoo( defaults )
println createFoo( defaults << [age:21] )
println createFoo( defaults << [ name:'Jane', address:'Low Street'] )

注意: leftShift操作(<<)修改原始地图,因此在上面的示例中,age也将在最后一次方法调用中为21.在我的情况下,这不是问题,因为每次在setup方法中都可以新创建默认映射.

Answer 1

Groovy默认为你做这件事(map构造函数).您不需要工厂方法.这是一个例子

import groovy.transform.ToString

@ToString(includeFields = true, includeNames = true)
class Foo{
    String name = "Default Name"
    int age = 25
    String address = "Default Address" 
}

println new Foo()
println new Foo(name: "John Doe")
println new Foo(name: "Max Payne", age: 30)
println new Foo(name: "John Miller", age: 40, address: "Omaha Beach")

//Prints
Foo(name:Default Name, age:25, address:Default Address)
Foo(name:John Doe, age:25, address:Default Address)
Foo(name:Max Payne, age:30, address:Default Address)
Foo(name:John Miller, age:40, address:Omaha Beach)

更新
@codelark的占星术:).如果无法访问类来设置默认值,您可以这样做

@ToString(includeFields = true, includeNames = true)
class Bar{
    String name
    int age
    String address
}

def createBar(Map map = [:]){
    def defaultMap = [name:'John Doe',age:51,address:'High Street 11']
    new Bar(defaultMap << map)
}

println createBar()
println createBar(name: "Ethan Hunt")
println createBar(name: "Max Payne", age: 30)
println createBar(name: "John Miller", age: 40, address: "Omaha Beach")


//Prints
Bar(name:John Doe, age:51, address:High Street 11)
Bar(name:Ethan Hunt, age:51, address:High Street 11)
Bar(name:Max Payne, age:30, address:High Street 11)
Bar(name:John Miller, age:40, address:Omaha Beach)