我們可以透過這些原則寫出能容忍變化、易於理解,且能被模組使用的良好「地基」
S = Single-responsibility principle (SRP) = 單一職責原則
O = Open–closed principle (OCP) = 開放封閉原則
L =Liskov substitution principle (LSP) = 里氏替換原則
I = Interface segregation principle (ISP) = 介面隔離原則
D = Dependency inversion principle (DIP) = 依賴反向原則