[[TableOfContents]]
= Chapter 10 Making Method Calls Simpler =
== Rename Method ==
The name of a method does not reveal its purpose. 
 ''Change the name of the method''

http://zeropage.org/~reset/zb/data/RenameMethod.gif

== Add Parameter ==
A method needs more information from its caller.
 ''Add a parameter for an object that can pass on this information''

http://zeropage.org/~reset/zb/data/AddParameter.gif
== Remove Parameter ==
A parameter is no longer used by the method body.
 ''Remove it''

http://zeropage.org/~reset/zb/data/RemoveParameter.gif
== Separate Query from Modifier ==
You have a method that returns a value but also changes the state of an object.
 ''Create two methods, one for the query and one for the modification''

http://zeropage.org/~reset/zb/data/SeparateQueryFromModifier.gif
== Parameterize Method ==
Several methods do similar things but with different values contained in the method body.
 ''Create one method that uses a parameter for the different values''

http://zeropage.org/~reset/zb/data/ParameterizeMethod.gif
== Replace Paramter with Explicit Method ==
You have a method that runs different code depending on the values of an enumerated parameter.
 ''Create a separate method for each value of the parameter''
{{{~cpp 
void setValue (String name, int value) {
	if (name.equals("height"))
		_height = value;
	if (name.equals("width"))
		_width = value;
	Assert.shouldNeverReachHere();
}
}}}

{{{~cpp 
void setHeight (int arg) {
	_height = arg;
}
void setWidth (int arg) {
	_width = arg;
}
}}}

== Preserve Whole Object ==
You are getting several values from an object and passing these values as parameters in a method call.
 ''Send the whole object instead''
{{{~cpp 
int low = daysTempRange().getLow();
int high = days.TempRange().getHight();
withinPlan = plan.withinRange (low, high);
}}}

{{{~cpp 
withinPlan = plan.withinRange (daysTempRange());
}}}

== Replace Parameter with Method ==
An object invokes a method, then passes the result as a parameter for a method. The receiver can also invoke this method.
 ''Remove the parameter and let the receiver invoke the method''
{{{~cpp 
int basePrice = _quantity * _itemPrice;
discountLevel = getDiscountLevel ();
double finalPrice = discountedPrice (basePrice, discountLevel);
}}}

{{{~cpp 
int basePrice = _quantity * _itemPrice;
double finalPrice = discountedPrice (basePrice);
}}}

== Introduce Parameter Object ==
You have a group of parameters that naturally go together.
 ''Replace them with an object''

http://zeropage.org/~reset/zb/data/IntroduceParameterObject.gif
== Remove Setting Method ==
A field should be set at creation time and never altered.
 ''Remove any setting method for that field''

http://zeropage.org/~reset/zb/data/RemoveSettingMethod.gif
== Hide Method ==
A method is not used by any other class.
 ''Make the method private''

http://zeropage.org/~reset/zb/data/HideMethod.gif
== Replace Constructor with Factory Method ==
You want to do more that simple construction when you create an object.
 ''Replace the constructor with a factory method''

{{{~cpp 
Emplyee (int type) {
	_type = type;
}
}}}

{{{~cpp 
static Emplyee create (int type) {
	return new Emplyee (type);
}
}}}

== Encapsulate Downcast ==
A method returns an object that needs to be downcasted by its callers.
 ''Move the downcast to within the method''
{{{~cpp 
Object lastReading () {
	return readings.lastElement ();
}
}}}

{{{~cpp 
Reading lastReading () {
	return (Reading) readings.lastElement ();
}
}}}

== Replace Error Code with Exception ==
A method returns a special code to indicate an error.
 ''Throw an exception instead''
{{{~cpp 
int withdraw(int amount) {
	if (amount > _balance)
		return -1;
	else {
		_balance -= amount;
		return 0;
	}
}
}}}


{{{~cpp 
void withdraw(int amount) throws BalanceException {
	if (amount > _balance) throw new BalanceException ();
	_balance -= amount;
}
}}}

== Replace Exception with Test ==
You are throwing an exception on a condition the caller could have checked first.
 ''Change the caller to make the test first''
{{{~cpp 
double getValueForPeriod (int periodNumber) {
	try {
		return _values[periodNumber];
	} catch (ArrayIndexOutOfBoundsException e) {
		return 0;
	}
}
}}}

{{{~cpp 
double getValueForPeriod (int periodNumber) {
	if (periodNumber >= _values.length) return 0;
	return _values[periodNumber];
}
}}}

----
["Refactoring"]