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Using python component in vue's script

Here is a first version. vbuild use and install pscript (it comes with vbuild for py2 and/or py3 ). pscript is used to transpile python to javascript version. A lot of python goodies are usable, but be sure to read the pscript caveats before.

VBuild needed to create a frame on how to declare a python component (because there was nothing yet, except that). This frame/definitions may evolve, but vbuild will understand the current and the future versions (based on how the class is defined), so the class Component: is the first usable version.

I've made a lot of trys, and this one is (IMO) the best (usefull and readable). I'm feeling more and more confortable using python component: life is better without braces ;-) (and syntaxic errors are sorted at compilation/rendering time)

Here is a working component which cover all of the current/implemented features :

  • Instanciate the data
  • props
  • Access to $attributes (works with $store/vuex)
  • Lifecycle events: created & mounted
  • computed field
  • watchers
<template>
    <div>
        {{name}} ({{originalName}})
        <button @click="inc(3)">+3</button>
        <button @click="inc()">+1</button>
        {{cpt}} : {{ccpt}} {{wcpt}}
    </div>
</template>
<script lang="python">
class Component:

    def __init__(self, name="?"):
        print("DATA INIT",name)
        self.cpt=0
        self.wcpt=""
        self.originalName=name  # copy the $props.name

    def inc(self,nb=1):                 # with py3, you can make this a async method !
        print("inc(%s)"%nb,self.name)
        self.cpt+=nb

    def CREATED(self):
        print("CREATED",self.name)

    def UPDATED(self):
        print("UPDATED",self.name)

    def MOUNTED(self):
        print("mounted",self.name,"in",self["$parent"]["$options"].name)
        self.inc()

    def COMPUTED_ccpt(self):
        print("COMPUTE",self.name,self.cpt,"changed")
        return self.cpt*"#"

    def WATCH_1(self,newVal,oldVal,name="cpt"):
        print("WATCH",self.name,name,oldVal,"-->",newVal)
        self.wcpt=self.cpt*"+"
        
    def WATCH_2(self,newVal,oldVal,name="name"):    # watch the prop !
        print("WATCH",name,oldVal,"-->",newVal)

</script>

With py3 : you can use async/await things in python methods (not in py2 !)

Features in details

By convention : lowercase methods are classic python methods, uppercase methods are special Vue's options. vbuild transpile the python class to a javascript one, and link methods in the vue's options. (I wanted to use "@decorators", but pscript doesn't support them (but in the future))

pscript needs to generate js wrapper to python functions : it's called the standard lib. You can choose to let vbuild generate the pscript standard lib, on the fly, for each component, or generate one standard lib for all, depending on your needs. (It could save bandswidth, if you have a lot of Python Components, to opt for the second option)

Just set vbuild.fullPyComp (boolean, 3 states), before vbuild.render'ing :

vbuild.fullPyComp=True  # (default) each components generate its needs.
vbuild.fullPyComp=False # minimal js transpilation, but vbuild will automatically include the "js standard lib" for you.
vbuild.fullPyComp=None  # minimal js transpilation, but it's up to you to include the js from "pscript.get_full_std_lib()".

Instanciate the data

Like in python, the initialization of the instance is done in the __init__(). In this statement, just init your data. All initialized properties will be used in the data options of the vue component (which will make them reactives).

(see def __init__(...) ^^)

props

The props are declared in the keywords of the __init__ statement. In the upper example, there is prop called 'name' ; so you can use the component like this :

<comp name="MyName"></comp>

The value of name will be passed when the __init__ statement is called (note that Vue will create a reactive property (self.name) after the __init__ call). But you can use the value of name to store it, in the data (like ^^ to keep the original value, for example)

If you use <comp></comp> without declaring the prop 'name', __init__ is called, and name will be undefined (Note that the reactive property self.name will not be created, in this case)

Access to $attributes

In all component's methods (except __init__()), you have access to $prefixed things using this syntax:

self["$parent"]
self["$store"].dispatch("myaction",payload)
self["$refs"].btnOk.click()
self["$forceUpdate"]()

Lifecycle events

Just create an uppercase method, with the name of the lifecyle ( "MOUNTED","CREATED","UPDATED","BEFOREUPDATE","BEFOREDESTROY","DESTROYED" )

(see def CREATED(self) and def MOUNTED(self) ^^)

Computed field

You can create a computed attibute, by declaring an instance method prefixed with "COMPUTED_", the method should return the computed value.

(see def COMPUTED_ccpt(self) ^^)

Watch'ers

You can create a whatcher on a vue attribute, by declaring an instance method prefixed with "WATCH_". This method should have the signature (self,newVal,oldVal,name="var_to_watch").

You should suffix your watch method, to make it unique. The name of the watch'ed attribute should be declared in the name argument.

(see def WATCH_1(...) and def WATCH_2(...) ^^)

Here are valid watchers :

def WATCH_1(self, newVal, oldVal, name="cpt"): pass
def WATCH_2(self, newVal, oldVal, name="$store.state.mylist"): pass

You can test that on vbuild's demo !

TODO:

  • ability to import things ?
  • use wrapper self._parent -> self["$parent"] ?
  • $store/vuex in python ? ($router/vue-router in python ?)