principles:liskov_substitution_principle
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principles:liskov_substitution_principle [2021-09-02 14:18] – old revision restored (2021-09-02 10:26) 65.21.179.175 | principles:liskov_substitution_principle [2021-10-18 21:50] – old revision restored (2018-05-27 18:40) christian | ||
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- | ====== Liskov Substitution Principle ====== | + | ====== Liskov Substitution Principle |
===== Variants and Alternative Names ===== | ===== Variants and Alternative Names ===== | ||
Line 6: | Line 6: | ||
===== Context ===== | ===== Context ===== | ||
/* fill in contexts here: */ | /* fill in contexts here: */ | ||
- | * [[contexts: | + | * [[contexts: |
+ | * [[contexts: | ||
===== Principle Statement ===== | ===== Principle Statement ===== | ||
+ | |||
+ | > " | ||
===== Description ===== | ===== Description ===== | ||
+ | Object-oriented programming languages permit the derivation of subtypes from base types, and subtype polymorphism allows the passing of an object of a subtype where ever an object of the supertype is specified. Suppose '' | ||
- | ===== Rationale ===== | + | The programming language does not enforce that the subtype behaves like the supertype. Method '' |
+ | |||
+ | |||
+ | ===== Rationale ===== | ||
+ | |||
+ | Let '' | ||
===== Strategies ===== | ===== Strategies ===== | ||
+ | |||
+ | * Only strengthen invariants in subclasses; never weaken them | ||
+ | * Only weaken preconditions when overriding methods | ||
+ | * Only strengthen postconditions when overriding methods | ||
+ | * Use Delegation instead of Inheritance | ||
+ | * Figure out better abstractions | ||
+ | |||
+ | ===== Caveats ===== | ||
+ | |||
+ | See section [[#contrary principles]]. | ||
===== Origin ===== | ===== Origin ===== | ||
+ | |||
+ | Barbara Liskov: // | ||
===== Evidence ===== | ===== Evidence ===== | ||
/* Comment out what is not applicable and explain the rest: */ | /* Comment out what is not applicable and explain the rest: */ | ||
- | /* | + | |
- | * [[wiki: | + | /* * [[wiki: |
- | * [[wiki: | + | |
- | * [[wiki: | + | * [[wiki: |
- | * [[wiki: | + | * [[wiki: |
- | */ | + | |
+ | /* * [[wiki: | ||
===== Relations to Other Principles ===== | ===== Relations to Other Principles ===== | ||
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==== Contrary Principles ==== | ==== Contrary Principles ==== | ||
- | * [[principles:Keep It Simple Stupid]] | + | * [[Keep It Simple Stupid]] |
==== Complementary Principles ==== | ==== Complementary Principles ==== | ||
- | * [[principles: | + | * [[Model Principle]] (MP): MP demands inheritance relations to resemble an " |
- | * [[principles: | + | * [[Principle |
==== Principle Collections ==== | ==== Principle Collections ==== | ||
Line 53: | Line 75: | ||
{{page> | {{page> | ||
- | ===== Example | + | |
+ | ===== Examples | ||
===== Description Status ===== | ===== Description Status ===== | ||
/* Choose one of the following and comment out the rest: */ | /* Choose one of the following and comment out the rest: */ | ||
- | [[wiki: | + | /*[[wiki: |
- | /*[[wiki: | + | [[wiki: |
/ | / | ||
+ | |||
===== Further Reading ===== | ===== Further Reading ===== | ||
- | * Robert C. Martin: //Agile Software Development, | + | * Robert C. Martin: //Agile Software Development, |
* [[http:// | * [[http:// | ||
+ | * [[wiki> | ||
+ | * [[wp> | ||
+ | * Barbara H. Liskov , Jeanette M. Wing: // | ||
+ | * Barbara H. Liskov , Jeanette M. Wing: // | ||
+ | |||
+ | ===== Discussion ===== | ||
+ | |||
+ | Discuss this wiki article and the principle on the corresponding [[talk: |
principles/liskov_substitution_principle.txt · Last modified: 2021-10-18 21:50 by christian