Groovy中@Delegate和@Mixin AST转换之间的区别 [英] Difference between @Delegate and @Mixin AST transformations in Groovy

问题描述

@Delegate 和 @ Mixin Groovy中的AST转换。

What's the difference between @Delegate and @Mixin AST transformations in Groovy.

也许我的问题与OO有关，当应用不同的模式时，但是我同时使用两者，我可以实现相同的行为。

Maybe my question has to do with OO and when apply different patterns, but I use both and I can achieve the same behavior.

class Person {
    String name = "Clark"
    def walk() { "Walk" }
}

@Mixin(Person)
class Superhero {
    def fly() { "Fly" }
}

def superman = new Superhero()
assert superman.name == "Clark"
assert superman.walk() == "Walk"
assert superman.fly() == "Fly"

---

---

class Person {
    String name = "Clark"
    def walk() { "Walk" }
}

class Superhero {
    @Delegate Person person
    def fly() { "Fly" }
}

def superman = new Superhero(person: new Person())
assert superman.name == "Clark"
assert superman.walk() == "Walk"
assert superman.fly() == "Fly"

推荐答案

行为是类似的，但 @Delegate 和 @Mixin 完全不同。

The behavior is similar, but @Delegate and @Mixin are implemented completely differently.

@Delegate 在编译时生成访问器方法。超级英雄将有一个名为 walk（）的方法，只需调用 person.walk（）。通过使用 javap 转储Superhero类文件可以看出生成的方法。

@Delegate generates accessor methods at compile time. Superhero will have a method called walk() that simply calls person.walk(). The generated methods can be seen by dumping the Superhero class file with javap.

@另一方面，Mixin 只是在运行时创建一个在 Person 方法中混合的小存根。它使用groovy的元对象协议来允许超级英雄回应人的方法。在这种情况下，您将不会在 Superhero.class 中看到任何Person方法。

@Mixin, on the other hand just creates a small stub that mixs in the Person methods at runtime. It uses groovy's meta-object protocol to allow Superhero to respond to Person's methods. In this case, you won't see any Person methods in Superhero.class.

@Delegate 的优点是可以从Java调用这些方法，并且避免了进行动态调用。另外， @Mixin 不能通过属性来增加类。

@Delegate has the advantage that the methods are callable from Java and it avoids doing a dynamic invocation. In addition, @Mixin can't augment the class with properties.

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