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Refactoring
Contents
- 1. Chapter 8 Organizing Data p169
- 1.1. Self Encapsulate Field p171
- 1.2. Replace Data Value with Object p175
- 1.3. Change Value to Reference p179
- 1.4. Change Reference to Value p183
- 1.5. Replace Array with Object p186
- 1.6. Duplicate Observed Data p189
- 1.7. Change Unidirectional Association to Bidirectional p197
- 1.8. Change Bidirectional Association to Unidirectional p200
- 1.9. Replace Magic Number with Symbolic Constant p204
- 1.10. Encapsulate Field p206
- 1.11. Encapsulate Collection p208
- 1.12. Replace Record with Data Class p217
- 1.13. Replace Type Code with Class p218
- 1.14. Replace Type Code with Subclasses p223
- 1.15. Replace Type code with State/Strategy p227
- 1.16. Replace Subclass with Fields p232
1.1. Self Encapsulate Field p171 ¶
- You are accessing a field directly, but the coupling to the field is becoming awkward.
Create getting and setting methods for the field and use only those to access the field.
~cpp
private int _low, _high;
boolean includes (int arg){
return arg >= _low && arg <= _high;
}
~cpp
private int _low, _high;
boolean includes (int arg){
return arg >= getLow() && arg <= getHigh();
}
int getLow() {return _low;}
int getHigh() {return _high;}
1.2. Replace Data Value with Object p175 ¶
- You have a data item that needs additional data or behavior.
Turn the data item into an object.
1.3. Change Value to Reference p179 ¶
- You have a class with many equal instances that you want to replace with a single object.
Turn the object into a reference object.
1.4. Change Reference to Value p183 ¶
- You have a reference object that is small, immutable, and awkward to manage.
Turn it into a balue object.
1.5. Replace Array with Object p186 ¶
- You have an array in which certain elements mean different things.
Replace the array with an object that has a field for each element.
~cpp
String[] row = new String[3];
row [0] = "Liverpool";
row [1] = "15";
~cpp
Performance row = new Performance();
row.setName("Liverpool");
row.setWins("15");
1.6. Duplicate Observed Data p189 ¶
- You have domain data available only in a GUI control, and domain methods need access.
Copy the data to a domain object. Set up an observer to synchronize the two pieces of data.
1.7. Change Unidirectional Association to Bidirectional p197 ¶
- You have two classes that need to use each other's features, but there is only a one-way link.
Add back pointers, and change modifiers to update both sets.
1.8. Change Bidirectional Association to Unidirectional p200 ¶
- You have a two-way associational but one class no longer needs features from the other.
Drop the unneeded end of the association.
1.9. Replace Magic Number with Symbolic Constant p204 ¶
- You have a literal number with a paricular meaning.
Crate a constant, name it after the meaning, and replace the number with it.
~cpp
double potentialEnergy(double mass, double height){
return mass * 9.91 * height;
}
~cpp
double potentialEnergy(double mass, double height){
return mass * GRAVITATION_CONSTNAT * height;
}
static final double GRAVITATIONAL_CONSTANT = 9,81;
1.10. Encapsulate Field p206 ¶
- There is a public field.
Make it private and provide accessors.
~cpp
public String _name;
~cpp
private String _name;
public String getName() {return _name;}
public void setName(String arg) { _name = arg;}
1.11. Encapsulate Collection p208 ¶
- A method return a collection.
Make it return a read-only view and provide add/remove methods.
1.12. Replace Record with Data Class p217 ¶
- You need to interface with a record structure in a traditional programming environment.
Make a dumb data object for the record.
1.13. Replace Type Code with Class p218 ¶
- A class has a numeric type code that does not affect its behavior.
Replace the number with a new class.
1.14. Replace Type Code with Subclasses p223 ¶
- You have an immutable type code that affects the bahavior of a class.
Replace the type code with subclasses.
1.15. Replace Type code with State/Strategy p227 ¶
- You have a type code that affects the behavior of a class, but you cannot use subclassing.
REplace the type code with a state object.
