Hi,

I'm sure someone can give a much better and more in-depth explanation but here goes:

1. Class side initialization is generally used to create fully functional objects. If you use just instance-side you might forget to set some important value (let's say ID) which would leave the object in invalid state. Another reason would be that it shows what does one really need to create a valid instance. If you have Empoyee class>>id: anId name: aName you will now know that salary is actually not needed and the object is able to cope with that. (And you can set it later). Yet another reason would be setting some additional/default values (however this can be done also internally on the instance-side).

2. Some elementary examples might be Rectangle or Point in Kernel > BasicObjects package. Generally you wouldn't send Employee message new directly, because that is class-side's job now, but rather you send the actual values: Employee id: 123 name: 'John Doe'. "answers with an Employee instance"

Peter

On Wed, Jul 23, 2014 at 8:33 AM, Dokania, Harshit <hdokani2@illinois.edu> wrote:

Hello,

I am creating an Object Relational Mapper in pharo using sqlite.

While creating database I am using a dictionary for columns of Database. This gives me Keys as column name and values as Data type of those.

So suppose Employee is the the table name, with ID->Integer, Name->Text, Salary->Float.

emp:= Employee new.
Now emp is a row of table, so for each row user has to create instance of Employee and then feed values to it. Later on he can pass message insert query to emp.

So I was creating this dictionary for column at the instance side initialization of Employee.

My instructor suggested to do that in class side initialization,

My Doubts are:

1. Why should we do class side initialization instead of instance side initialization.

2. Could you please refer me to the link which explains how to do class side initialization. Because when I do Employee new, I see only instance side initialization is being called.

Thanks,
Harshit