difference between method and ClassMethod of Class definition

Question

Question

Ponnumani Gurusamy · Sep 15, 2016

#Object Data Model #Caché

What are the difference between method() and ClassMethod() in Cache Class definition

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Yuval Golan · Sep 15, 2016

Method() is at the object level (the instance of the class) and ClassMethod() is at the class level .

Lets say that we have a Car class then:

Method PrintCar() {

//print the car number

}

ClassMethod PrintAllCars() {

//for each car call it's PrintCar()

}

0 0

score 3 · Answer 1 · 2016-09-15T05:47:38-04:00

Caché Programming Orientation Guide explains this in details. Please read:
http://docs.intersystems.com/latest/csp/docbook/DocBook.UI.Page.cls?KEY=...

score 1 · Answer 2 · 2016-09-15T08:26:39-04:00

As a consequence of the previous answers it is not allowed to address instance properties using the "dot dot" syntax within a class method. Using the previous example: it is ok to use

set tCarNumber=..CarNumber

within the PrintCar() method (providing there is a CarNumber property defined)

but you cannot use it in ClassMethod - as a class method can be called outside of any instance context.

score 1 · Answer 3 · 2016-09-15T10:57:41-04:00

method() is an instance method; you need a car object in order to call it.

set car = ##class(Car).%New()

d car.PrintCar()

ClassMethod() you dont' need an object (provided it's not private).

d ##class(Car).PrintAllCars()

If you know Java, ClassMethod is like a static method; method is like an instance method.

score 1 · Answer 4 · 2016-09-15T11:44:29-04:00

The doc. has an section on this:

" There are two kinds of methods in a class language: instance methods and class methods. These have different purposes and are used in different ways...."

http://docs.intersystems.com/latest/csp/docbook/DocBook.UI.Page.cls?KEY=GORIENT_ch_classprog#GORIENT_classprog_method

I hope this helps.