"Dan Ackroyd" wrote in message
news:ca+kxmusl1kew60s7dfjb06+r2q3rc1ueewu1jap78fy65aj...@mail.gmail.com...
On 6 September 2017 at 13:31, Rowan Collins <rowan.coll...@gmail.com>
wrote:
I'm going to assume that the code you posted was something of a straw
man, and you're not actually advocating people copy 20 lines of code for
every variable they want to validate.
You assume wrong. No it's not, and yes I am.
I can point a junior developer at the function and they can understand it.
If I ask that junior developer to add an extra rule that doesn't
currently exist, they can without having to dive into a full library
of validation code.
If I need to modify the validation based on extra input (e.g whether
the user has already made several purchases, or whether they're a
brand new signup), it's trivial to add that to the function.
This is one of the times where code re-use through copying and pasting
is far superior to trying to make stuff "simple" by going through an
array based 'specification'. It turns out that that doesn't save much
time to begin with, and then becomes hard to manage when your
requirements get more complication.
As a person who has been developing database applications for several
decades and with PHP since 2003 I'd like to chip in with my 2 cent's worth.
Firstly I agree with Dan's statement:
This type of library should be done in PHP, not in C.
Secondly, there is absolutely no way that you can construct a standard
library which can execute all the possible validation rules that may exist.
In my not inconsiderable experience there are two types of validation:
1) Primary validation, where each field is validated against the column
specifications in the database to ensure that the value can be written to
that column without causing an error. For example this checks that a number
is a number, a data is a date, a required field is not null, etc.
2) Secondary validation, where additional validation/business rules are
applied such as comparing the values from several fields. For example, to
check that START_DATE is not later tyhan END_DATE.
Primary validation is easy to automate. I have a separate class for each
database table, and each class contains an array of field specifications.
This is never written by hand as it is produced by my Data Dictionary which
imports data from the database schema then exports that data in the form of
table class files and table structure files. When data is sent to a table
class for inserting or updating in the database I have written a standard
validation procedure which takes two arrays - an array of field=value pairs
and a array of field=specifications - and then checks that each field
conforms to its specifications. This validation procedure is built into the
framework and executed automatically before any data is written to the
database, so requires absolutely no intervention by the developer.
Secondary validation cannot be automated, so it requires additional code to
be inserted into the relevant validation method. There are several of these
which are defined in my abstract table class and which are executed
automatically at a predetermined point in the processing cycle. These
methods are defined in the abstract class but are empty. If specific code is
required then the empty class can be copied from the abstract class to the
concrete class where it can be filled with the necessary code.
If there are any developers out there who are still writing code to perform
primary validation then you may learn something from my implementation.
If there are any developers out there who think that secondary validation
can be automated I can only say "dream on".
--
Tony Marston
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