Design problem

[Juan Pablo]

Hi.
I have 3 objects. Object INTERFACEDAT will interact with plain text
files and retrieve some kind of recordset/collection, a FIELDS object,
which will be populated with FIELD objects. From the main module I
want to retrieve a collection of FIELDS so I need to include the 3
classes. This seems good because main needs to know these 3 classes.
But how can avoid, for example, creating an instance of FIELDS
directly in main module, I mean, I want only INTERFACEDAT to create
this kind of object. The same applies to FIELD object. How can I
restrict the creation of these to objects to INTERFACEDAT, how can
avoid from main doing this (field* f = new field?
Thank you in advance

Juan Pablo Polotto

 

[Karl Heinz Buchegger]

Hi.
I have 3 objects. Object INTERFACEDAT will interact with plain text
files and retrieve some kind of recordset/collection, a FIELDS object,
which will be populated with FIELD objects. From the main module I
want to retrieve a collection of FIELDS so I need to include the 3
classes. This seems good because main needs to know these 3 classes.
But how can avoid, for example, creating an instance of FIELDS
directly in main module, I mean, I want only INTERFACEDAT to create
this kind of object. The same applies to FIELD object. How can I
restrict the creation of these to objects to INTERFACEDAT, how can
avoid from main doing this (field* f = new field?
Thank you in advance

By making the constructor of FIELD private or protected.
Nobody can then create an object of that class type, except
an INTERFACEDAT object, which you declare to be a friend of FIELD.

 

[jeffc]

Hi.
I have 3 objects. Object INTERFACEDAT will interact with plain text
files and retrieve some kind of recordset/collection, a FIELDS object,
which will be populated with FIELD objects. From the main module I
want to retrieve a collection of FIELDS so I need to include the 3
classes. This seems good because main needs to know these 3 classes.
But how can avoid, for example, creating an instance of FIELDS
directly in main module, I mean, I want only INTERFACEDAT to create
this kind of object. The same applies to FIELD object. How can I
restrict the creation of these to objects to INTERFACEDAT, how can
avoid from main doing this (field* f = new field?

If you really want to restrict it, with code, then you can make the
constructor private. Then you can make INTERFACEDAT a friend of FIELD.

 

[Juan Pablo]

By making the constructor of FIELD private or protected.
Nobody can then create an object of that class type, except
an INTERFACEDAT object, which you declare to be a friend of FIELD.

Thank you all for your quick responses.