Question

I have a map which says maps a string to a function like :

validator = {'first_name' : validate_str,
             'last_name' : validate_str,
             'phone' : validate_phone }

I need to call the corresponding validate function based on the type of value I have in the map that will be fed to me as input for e.g.

for name in elements:
    # Validate the value of this name in the input map using the function
    # input is the map that has the value for each of these fields
    # elements is a list of all fields used to loop through one input at a time
    if validator[name]( input[name] ) is False:
        # Throw validation error
    else:
        # Do something else

This works fine unless for this scenario I am not sure if it can be done:

The validate_str also checks if a given string is of desired max length.

def validate_str(str, max-len):
    # Throw error if len(str) > max-len

The max-len can differ based on the string, so I need to call validate_str for first_name with say 64 characters and last name with 256 characters.

I can use a different map to say that this field has this max_len, but is it possible for the validator map to have pointer to the validate_str function with the max-len argument preset based on the field?

something like:

validator = {'first_name' : validate_str(max-len=64),
             'last_name' : validate_str(max-len=256),
             'phone' : validate_phone }

then call it for validation like:

if validator[name]( str=input[name] ) is False:
    # The appropriate value for max-len goes with the function call and just the
    # str is appended to the argument list while invoking. 

This makes life easier so that we need not then remember again what fields will have the max-len sent along with it.

Answer 1

You could use lambda to create a function of one argument (the string being validated) but has the length defined within in:

{'first-name':lambda x: validate-str( x, 64 ), ...