Groovy擴展hashmap與字段

Question

這是行不通的。不應該嗎？

class WeirdBean extends HashMap { 
    public String inner = "set within" 
    def getInner() { return this.inner } 
    def getOuter() { return this.outer } 
} 

def o = WeirdBean.newInstance() 
o.outer = "set without" 
println o.getOuter() // set without 
println o.outer  // set without 
assert o.outer == o.getOuter() // Pass 

println o.getInner() // set within 
println o.inner  // null, even though public 
assert o.inner == o.getInner() // Fail, o.inner is null 

Answer 1

好像Map::get比object.field或object.property更高的優先級。因爲裏面的字段訪問一個類不通過getter，這個工作：

class WeirdBean extends HashMap { 
    public String inner = "set within" 
    def getInner() { return this.inner } 

    def getProperty(String property) { 
    (property == 'inner') ? inner : super.get(property) 
    } 

    def getOuter() { return this.outer } 
} 

def o = WeirdBean.newInstance() 
o.outer = "set without" 
println o.getOuter() // set without 
println o.outer  // set without 
assert o.outer == o.getOuter() // Pass 

println o.getInner() // set within 
println o.inner  // null, even though public 
assert o.inner == o.getInner() // Fail, o.inner is null 

Answer 2

表達式o.inner從HashMap返回鍵。有沒有這樣的關鍵inner所以會返回空值，而裏面this.inner場的getInner()方法返回值是（被設定爲"set without"。這就是爲什麼。