[Tutor] Simulating case statement

[Jan Eden]

Hi,

I used to use an extended if...elif sequence to instantiate an object and call this object's display method afterwards:
####
if safe['type'] == pages:
    page = Show.Page(id=safe['id'], start=safe['start'] ...),
elif safe['type'] == pages:
    author = Show.Author(id=safe['id']...)
 ...

page.Display()
#### 

To improve readability, I changed this code to use a dictionary:

####
valid_types = dict(
    pages=Show.Page,
    authors=Show.Author,
    ...
)

page = valid_types[safe_parameters['type']](safe_parameters)
page.Display()
####

The problem is that the __init__ methods of the respective classes take a different number of parameters - this is why I pass the whole safe_parameters dictionary.

This has a number of drawbacks when instantiating an object in other situations because I cannot use a default for some parameters while passing some others.

So I'd like to do pass the parameters individually, based on the class. I know I would need to expand the valid_types dictionary to include the parameters - but how can I pass these one by one?

What I came up with is a monster (which does not work anyway):

valid_types = dict(
    pages=dict(klasse=Show.Page, parameters=dict(id=safe['id'], start=safe['start'] ...))
    authors=dict(klasse=Show.Author, ...)
    ...
)

page = valid_types[safe_parameters['type']]['klasse'](valid_types['parameters'])

page.Display()

How can I circumvent the if...elif sequence and have the parameters passed individually at the same time?

Thanks for any suggestions,

Jan
-- 
Common sense is what tells you that the world is flat.