测试
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分类: 架构设计与优化
2019-04-13 15:28:32
如果constructor里调用了一个成员方法,这个方法被子类override了,当初始化一个子类实例时,父类的构造函数被的调用,此时父类构造函数的上下文里调用的成员方法,是父类的实现还是子类的实现?
你能不用运行代码,就能准确说出这些语句会打印什么出来呢?
class ZCL_SUPER definition public
create public .
public section.
methods CONSTRUCTOR .
methods SET_I
importing
!IV_I type INT4 .
protected section.
private section.
data MV_SUPER type INT4 .
ENDCLASS.
CLASS ZCL_SUPER IMPLEMENTATION.
method CONSTRUCTOR.
me->set_i( 100 ).
endmethod.
method SET_I.
me->mv_super = iv_i.
endmethod.
ENDCLASS. class ZCL_SUB definition public
inheriting from ZCL_SUPER
final
create public .
public section.
methods PRINT .
methods SET_I
redefinition .
protected section.
private section.
data MV_SUB type I value 1 ##NO_TEXT. ENDCLASS.
CLASS ZCL_SUB IMPLEMENTATION.
method PRINT. WRITE: / ' sub:' , mv_sub.
endmethod.
METHOD set_i. super->set_i( iv_i = iv_i ).
me->mv_sub = iv_i. WRITE: / 'mv_sub assigned by: ' , iv_i.
ENDMETHOD.
ENDCLASS.
测试:
NEW zcl_sub( )->print( ).
测试结果:sub: 1
public class SuperClass { private int mSuperX; public SuperClass() {
setX(99);
} public void setX(int x) {
mSuperX = x;
}
} public class SubClass extends SuperClass { private int mSubX = 1; public SubClass() {} @Override public void setX(int x) { super.setX(x);
mSubX = x;
System.out.println("SubX is assigned " + x);
} public void printX() {
System.out.println("SubX = " + mSubX);
}
}
test:
public static void main(String[] args) {
SubClass sc = new SubClass();
sc.printX();
}
测试结果:
function SuperClass(){ this.setX(99);
}
SuperClass.prototype = { mSuperX : 0, setX : function(x){ this.mSuperX = x;
}
}; function SubClass(){
SuperClass.call(this); this.mSubX = 1;
}
SubClass.prototype = new SuperClass();
SubClass.prototype.setX = function(x){
SuperClass.prototype.setX(x); this.mSubX = x; console.log("SubX is assigned " + x);
};
SubClass.prototype.print = function(){ console.log("SubX: " + this.mSubX);
}
test:
var sub = new SubClass();
sub.print();
测试结果:
详细分析在我的SAP community博客里: A reminder for using constructor in OO world
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