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Learning TypeScript 2.x - Second Edition
book

Learning TypeScript 2.x - Second Edition

by Remo H. Jansen
April 2018
Beginner content levelBeginner
536 pages
13h 21m
English
Packt Publishing
Content preview from Learning TypeScript 2.x - Second Edition

SOLID – the Liskov substitution principle 

The Liskov substitution principle (LSP) states, Subtypes must be substitutable for their base types. Let's look at an example to understand what this means.

We will declare a class named PersistanceService, the responsibility of which is to persist some object into some sort of storage. We will start by declaring the following interface:

interface PersistanceServiceInterface { 
    save(value: string): string; 
} 

After declaring the PersistanceServiceInterface interface, we can implement it. We will use cookies as the storage for the application's data:

function getUniqueId() { return Math.random().toString(36).substr(2, 9); } class CookiePersitanceService implements PersistanceServiceInterface { public ...
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Publisher Resources

ISBN: 9781788391474Supplemental Content