@escript decorator and magic methods 🔮

Magic @escript decorator

@escript decorator is a method-decorator, that is used for decorating methods of "epurized" (1) class

1. "epurized" class is class that was decorated by @epure() decorator

@escript decorator magicly convert your queries into strings

@escript decorator with @classmethod decorator

...
@classmethod
@escript
def your_method():
...

Info

Only in method decorated by @escript, can be used instances of self.dom, self.md and method self.model

Lets see an example:

Alien Cats example 👽🐈

Retrieving cats with more than one tail using @escript

For example you have a class Cat:

@epure()
class Cat:
    paws_cntr:int
    name:str
    tail_cntr:int
    likes_catnip:bool

And you want to get all the stored cats:

• with more than one tail (lets assume there are some cat-alien species 👽)

• and those cats who don't like catnip (a real weird cat-aliens)

Then we will define a method for class Cat decorated by @escript:

...
@classmethod
@escript
def get_all_cats_with_two_tails(cat):

    my_query = cat.md.tail_cntr > 1 and cat.md.likes_catnip == False

    res = cat.resource.read(my_query)

    res # [<Cat object at 0x000001FFFC6800D0>, <Cat object at 0x000001FCFC6800D7>, ...]

...

Let's look closely to my_query:

...
my_query = cat.md.tail_cntr > 1 and cat.md.likes_catnip == False
...

First, because method is a classmethod, in cat variable will be assigned class.

Then we are taking .md Model of Cat class and taking Column tail_cntr and comparing it to more than 1

In resulting list we will get cats with more than one tail and those who doesnt like catnip. Like expected!

What will be result SQL of this query

SELECT * 
FROM public.cat 
WHERE cat.tail_cntr > 1 AND cat.likes_catnip = False

All avalible for self.md methods

All the avalible methods (e.g. ==, like, is_not, _is etc), for self.md can be found in Column Proxy methods section

More Advanced Alien Cats 👽🐈 example with for

So if we want to create something more complex, lets use for statement:

Creating advanced smart query with for

So as in previous example you have a class Cat:

@epure()
class Cat:
    paws_cntr:int
    name:str
    tail_cntr:int
    likes_catnip:bool

But this time you want to get Cat(s) that:

• has a tail (i.e tail_cntr is not `#!sql NULL``)
• has a name and name starts with letter 'C'
• has less than 5 paws or equally 8 paws (more like an octocat )
• likes catnip 🍀

So we will define magic method for Cat class:

...
@classmethod
@escript
def get_cats_using_for(cat):

    has_tail_query = cat.md.tail_cntr is not None

    name_query = cat.md.name is not None and cat.md.name.like("C%")

    legs_query = cat.md.paws_cntr < 5 or cat.md.paws_cntr == 8

    catnip_query = cat.md.likes_catnip == True

    ...

After we created our queries, imagine: we want all to this conditions to meet and be True at the same time.

But what do we do? 🤔

Create a long-long query, that is unreadable and to much hassle to edit? Nah ❌.

I suggest to use for loop ✔️.

This way, we can put them in a list and iterate over it adding and to each condition, sticking it all together

    ...
    queries_list = [name_query, legs_query, catnip_query, has_tail_query]

    result_query = True

    for query in queries_list:
       result_query = result_query and query

    res = cat.resource.read(result_query)

    res # [<Cat object at 0x000001FFFC6800D0>, <Cat object at 0x000001FCFC6800D7>, ...]

line 18 result_query = has_tail_query explanation

This assignemnt made mainly made because we need to start somewhere and we cant use empty string ("") as a start.

This way we will get a long smart query without any hassle and code confusion.