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"source": [
"# Adapter Pattern\n",
"The purpose is to present a client code with abstract api, rather than a number of different apis with similar goals\n",
"1. Favours to program abstraction rather than to concrete objects (D - Dependency Inversion)\n",
"1. Open Closed principle (O)\n",
"1. Used to convert interface of a class into one that client expects\n",
"\n",
"> **Example**\n",
"> - AC Adapters\n",
"> - Pipe Adapter\n",
"> - US - India Power Sockets\n",
"\n",
"> Also Known As the Wrapper Pattern"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"# A program made to Print Customer Name and Address\n",
"1. Later on in project, we're asked to make it work for Vendor object\n",
"1. Unfortunately, currently they are different APIs - Vendor (Street and Number diff) - Customer (Combined Address Property)\n",
"1. Can't just copy and paste the Customer Name printer object, it would violate (DRY - Don't Repeat Yourself!)\n",
"1. Add some conditional logic, to handle both prints - (Worthless!)"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"# 2 Types\n",
"1. Object adapter - Composition - Can easily work with both parent and child class\n",
"1. Class adapter - Inheritance - It lets the Adapter override some of the classes methods\n",
"\n",
"> **Favour Composition over Inheritance always!**\n",
"> - It leads to flatter class structure\n",
"> - Easy to understand, Debug and Maintain"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"# Object Adapter"
]
},
{
"cell_type": "code",
"execution_count": 1,
"metadata": {
"collapsed": true
},
"outputs": [],
"source": [
"from abc import ABCMeta, abstractproperty"
]
},
{
"cell_type": "code",
"execution_count": 2,
"metadata": {
"collapsed": true
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"outputs": [],
"source": [
"class Customer():\n",
" def __init__(self, name, address):\n",
" self._name = name\n",
" self._address = address\n",
" \n",
" @property\n",
" def name(self):\n",
" return self._name\n",
" \n",
" @property\n",
" def address(self):\n",
" return self._address"
]
},
{
"cell_type": "code",
"execution_count": 3,
"metadata": {},
"outputs": [],
"source": [
"MOCK_CUSTOMERS = (\n",
" Customer('Pizza Love', '33 Peperoni Lane'),\n",
" Customer('Happy and Green', '25 Kale St.'),\n",
" Customer('Sweet Tooth', '42 Chocolate Ave.')\n",
")"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Adaptee"
]
},
{
"cell_type": "code",
"execution_count": 4,
"metadata": {
"collapsed": true
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"outputs": [],
"source": [
"class Vendor():\n",
" def __init__(self, name, number, street):\n",
" self._name = name\n",
" self._number = number\n",
" self._street = street\n",
" \n",
" @property\n",
" def name(self):\n",
" return self._name\n",
" \n",
" @property\n",
" def number(self):\n",
" return self._number\n",
" \n",
" @property\n",
" def street(self):\n",
" return self._street"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Adapter"
]
},
{
"cell_type": "code",
"execution_count": 5,
"metadata": {
"collapsed": true
},
"outputs": [],
"source": [
"class IAdapter(metaclass=ABCMeta):\n",
" def __init__(self, adaptee):\n",
" self._adaptee = adaptee\n",
" \n",
" @property\n",
" def adaptee(self):\n",
" return self._adaptee\n",
" \n",
" @abstractproperty\n",
" def name(self):\n",
" pass\n",
" \n",
" @abstractproperty\n",
" def address(self):\n",
" pass"
]
},
{
"cell_type": "code",
"execution_count": 6,
"metadata": {
"collapsed": true
},
"outputs": [],
"source": [
"class VendorAdapter(IAdapter):\n",
" @property\n",
" def name(self):\n",
" return self.adaptee.name\n",
" \n",
" @property\n",
" def address(self):\n",
" return f'{self.adaptee.number} {self.adaptee.street}'"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"## Composition"
]
},
{
"cell_type": "code",
"execution_count": 7,
"metadata": {},
"outputs": [],
"source": [
"MOCK_VENDORS = (\n",
" VendorAdapter(Vendor('Dough Factory', 1, 'Semolina Court')),\n",
" VendorAdapter(Vendor('Farm Produce', 14, 'Country Rd.')),\n",
" VendorAdapter(Vendor('Cocoa World', 53, 'Tropical Blvd.'))\n",
")"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"# Print works for both Customers and Vendors"
]
},
{
"cell_type": "code",
"execution_count": 8,
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"Name: Pizza Love, Address: 33 Peperoni Lane\n",
"Name: Happy and Green, Address: 25 Kale St.\n",
"Name: Sweet Tooth, Address: 42 Chocolate Ave.\n"
]
}
],
"source": [
"CUSTOMERS = MOCK_CUSTOMERS\n",
"\n",
"for cust in CUSTOMERS:\n",
" print(f'Name: {cust.name}, Address: {cust.address}')"
]
},
{
"cell_type": "code",
"execution_count": 9,
"metadata": {},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"Name: Dough Factory, Address: 1 Semolina Court\n",
"Name: Farm Produce, Address: 14 Country Rd.\n",
"Name: Cocoa World, Address: 53 Tropical Blvd.\n"
]
}
],
"source": [
"CUSTOMERS = MOCK_VENDORS\n",
"\n",
"for cust in CUSTOMERS:\n",
" print(f'Name: {cust.name}, Address: {cust.address}')"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"# Class Adapter\n",
"1. Inherits both classes, and then modifies"
]
},
{
"cell_type": "code",
"execution_count": 10,
"metadata": {
"collapsed": true
},
"outputs": [],
"source": [
"class VendorAdapter(Vendor, Customer):\n",
" def __init__(self, *args, **kwargs):\n",
" super().__init__(*args, **kwargs)\n",
" \n",
" @property\n",
" def address(self):\n",
" return f'{self.number} {self.street}'"
]
},
{
"cell_type": "code",
"execution_count": 11,
"metadata": {
"collapsed": true
},
"outputs": [],
"source": [
"MOCK_VENDORS = (\n",
" VendorAdapter('Dough Factory', 1, 'Semolina Court'),\n",
" VendorAdapter('Farm Produce', 14, 'Country Rd.'),\n",
" VendorAdapter('Cocoa World', 53, 'Tropical Blvd.')\n",
")"
]
},
{
"cell_type": "code",
"execution_count": 12,
"metadata": {
"scrolled": true
},
"outputs": [
{
"name": "stdout",
"output_type": "stream",
"text": [
"Name: Dough Factory, Address: 1 Semolina Court\n",
"Name: Farm Produce, Address: 14 Country Rd.\n",
"Name: Cocoa World, Address: 53 Tropical Blvd.\n"
]
}
],
"source": [
"CUSTOMERS = MOCK_VENDORS\n",
"\n",
"for cust in CUSTOMERS:\n",
" print(f'Name: {cust.name}, Address: {cust.address}')"
]
},
{
"cell_type": "markdown",
"metadata": {},
"source": [
"# Pros and Cons\n",
"**Object Adapter**\n",
"1. Composition over Inheritance\n",
"1. Delegates to Adaptee\n",
"1. Works with all adaptee subclasses (If they don't change) - Open Close Principle maybe broken\n",
"\n",
"**Class Adapter**\n",
"1. Subclassing\n",
"1. Overrides Adaptee's methods"
]
}
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