Refactoring Notes-Refactoring Methods(3)
来源:互联网 发布:怎么利用淘宝客买东西 编辑:程序博客网 时间:2024/04/30 01:51
5.Introduce Explaining Variable
If you have a complicated expression,put the result of the expression, or parts of the expression , in a temporary variable with a name that explains the purpose.
Introduce Explaining Variable is particulaly valuable with conditional logic in which it is useful to take each clause of a condition and explain what the condition means a well-named temp.
Another case is a long algorithm,in which each step in the computation can be explained with a temp.
Mechanics
(1)Declare a final temporary variable,and set it to the result of part of the complex expression.
(2)Replace the result part of the expression with the value of the temp.
Before:
double price(){
return quantity*itemPrice-Math.max(0,quantity-500)*itemPrice*0.05+Math.min(quantity*itemPrice*0.1,100.0);
}
After:
double price(){
final double basePrice= quantity*itemPrice;
final double quantityDiscount=Math.max(0,quantity-500)*itemPrice*0.05 ;
final double shipping=Math.min(quantity*itemPrice*0.1,100.0);
return basePrice-quantityDiscount+shipping;
}
Appendix: using Extract Method to complete refactoring.
The benefit of using Extract Method is that theses methodologies are available to any other part of the object that needs them.Although they are private at first,but you can relax that if another object needs them.
double price(){
return basePrice()-quantityDiscount()+shipping();
}
private Double basePrice(){
return quantityDiscount*itemPrice;
}
private Double quantityDiscount(){
return Math.min(quantity*itemPrice*0.1,100.0);
}
private Double shipping(){
return Math.min(quantity*itemPrice*0.1,100.0);
}
6.Split Temporary Variable
If a temporary variable assigned to more than once,but is not a loop variable nor a collecting temporary variable(If the later assignments are of the form i=i+some expression, that indicates that it is a collceting temporary variable),you should use Split Temporary Method.Any variable with more than one responsibility should be replaced with a temp for each responsibility.
Michanics:
(1)Change the name of a temp at its declaration and its first assignment.
(2)Declare the new temp as final.
(3)Change all references of the temp up to its second assignment.
(4) Declare the temp at its second assignment.
Before:
double getDistanceTravelled(int time){
double result;
double acc=primaryForce/mass;
int primaryTime=Math.min(time,delay);
result = 0.5*acc*primaryTime*primaryTime;
int secondaryTime=time-delay;
if(secondaryTime>0){
double primaryVel=acc*delay;
acc=(primaryForce+secondaryForce)/mass;
result+=primaryVel*secondaryTime+0.5*acc*secondaryTime*secondaryTime;
}
return result;
}
After:
double getDistanceTravelled(int time){
double result;
final double primaryAcc=primaryForce/mass;
int primaryTime=Math.min(time,delay);
result = 0.5*primaryAcc*primaryTime*primaryTime;
int secondaryTime=time-delay;
if(secondaryTime>0){
double primaryVel=primaryAcc *delay;
final double secondaryAcc=(primaryForce+secondaryForce)/mass;
result+=primaryVel*secondaryTime+
0.5*secondaryAcc*secondaryTime*secondaryTime;
}
return result;
}
Appendix: Complete refactoring
double getDistanceTravelled(int time){
double result;
result = 0.5*getPrimaryAcc()*Math.pow(getPrimaryTime(time),2);
if(getSecondaryTime(time)>0){
double primaryVel=getPrimaryAcc() *delay;
final double secondaryAcc=(primaryForce+secondaryForce)/mass;
result+=primaryVel*getSecondaryTime(time)+
0.5*secondaryAcc*Math.pow(getSecondaryTime(time),2);
}
return result;
}
private int getPrimaryTime(int time){
return Math.min(time,delay);
}
private double getPrimaryAcc(){
return primaryForce/mass;
}
private int getSecondaryTime(int time){
return time-delay;
}
7.Remove Assignments to Parameters
Before:
int discount(int inputVal, int quantity, int yearToDate){
if(inputVal>50) inputVal-=2;
if(quantity>100) inputVal-=1;
if(yearToDate>10000) inputVal-=4;
return inputVal;
}
After:
int discount(int inputVal, int quantity, int yearToDate){
int result=inputVal;
if(inputVal>50) result-=2;
if(quantity>100) result-=1;
if(yearToDate>10000) result-=4;
return result;
}
8.Replace Method with Method Object
If there is a long method that uses local variables in such a way that you cannot apply Extract Method.Turn the mothod into its own object so that all the local variables became fields on that object.You can then decompose the method into other methods on the same object.
Michanics:
(1)Create a new class ,name it after the method.
(2)Give the new class a final field for the object that hosted the original method and a field for each temporary variable and each parameter int the method.
(3)Give the new class a constructor that takes the source object and each parameter.
(4)Give the new class a method named “compute” and copy the body of the original method into it.
Before:
class Account{
int gamma(int inputVal,int quantity,int yearToDate){
int importantVal1=(inputVal*quantity)+delta();
int importantVal2=(inputVal*yearToDate)+100;
if((yearToDate-importantVal1>100))
importantVal2-=20;
int importantVal3=importantVal2*7;
return importantVal3-2*importantVal1;
}
}
After:
class Account{
int gamma(int inputVal,int quantity,int yearToDate){
return new Gamma(this, inputVal, quantity, yearToDate);
}
}
class Gamma{
public Gamma(Account account,int inputVal,int quantity,int yearToDate){
account=account;
inputVal=inputVal;
quantity=quantity;
yearToDate=yearToDate;
}
final Account account;
int importantVal1;
int importantVal2;
int importantVal3;
int inputVal;
int quantity;
int yearToDate;
int compute(){
int importantVal1=(inputVal*quantity)+account.delta();
int importantVal2=(inputVal*yearToDate)+100;
if((yearToDate-importantVal1>100))
importantVal2-=20;
int importantVal3=importantVal2*7;
return importantVal3-2*importantVal1;
}
}
9.Substitue Algorithm
Replace an algorithm with one that is clearer.
- Refactoring Notes-Refactoring Methods(3)
- Refactoring Notes-Refactoring Methods
- Refactoring Notes-Refactoring Methods(2)
- Refactoring
- Refactoring
- Refactoring
- Refactoring
- Refactoring notes 20120105
- Refactoring notes 20120106
- Refactoring to Patterns Review 3
- Refactoring HiMock
- Refactoring practice
- About Refactoring
- Refactoring Workbook
- Refactoring 笔记
- Refactoring Session
- Refactoring Memo
- Refactoring 网站
- 俏也不争春――走近电子网络游戏(上)
- 该下班时就下班,何必不好意思呢
- 关于html编辑器的回车换行问题解决方案
- 烦闷!但也是新的开始,越来越对GameCracking感兴趣了!
- html编辑器中得到系统的字体
- Refactoring Notes-Refactoring Methods(3)
- 《设计模式Design Pattern》读书笔记之十三
- java.lang.IllegalMonitorStateException翻译
- Html编辑器控件(ASP.NET)收集
- 声明
- 职业生涯规划
- 找工作
- [转]2004手机游戏年终点评
- SAS技巧-关于速度改进的小技巧,来源于BOSS技术语录