重构指南 - 封装条件（Encapsulate Conditional）

封装就是将相关的方法或者属性抽象成为一个对象。

封装的意义：

1. 对外隐藏内部实现，接口不变，内部实现自由修改。
2. 只返回需要的数据和方法。
3. 提供一种方式防止数据被修改。
4. 更好的代码复用。

 

当代码中包含许多条件判断，为了改善代码的可读性和可维护性，我们可以将条件封装。

有两种封装方式：

一、无参数的条件判断，封装为属性

 

重构前代码

public class RemoteControl
    {
        private string[] Functions { get; set; }
        private string Name { get; set; }
        private int CreatedYear { get; set; }

        public string PerformCoolFunction(string buttonPressed)
        {
            // Determine if we are controlling some extra function
            // that requires special conditions
            if (Functions.Length >  && Name == "RCA" && CreatedYear > DateTime.Now.Year - )
                return "doSomething";
        }
    }

重构后代码

public class RemoteControl
    {
        private string[] Functions { get; set; }
        private string Name { get; set; }
        private int CreatedYear { get; set; }

        private bool HasExtraFunctions
        {
            get { return Functions.Length >  && Name == "RCA" && CreatedYear > DateTime.Now.Year - ; }
        }

        public string PerformCoolFunction(string buttonPressed)
        {
            // Determine if we are controlling some extra function
            // that requires special conditions
            if (HasExtraFunctions)
                return "doSomething";
        }
    }

二、有参数的条件判断，封装为方法

 

重构前代码

 public class RemoteControl
    {
        private string[] Functions { get; set; }
        private int CreatedYear { get; set; }

        public string PerformCoolFunction(string buttonPressed)
        {
            // Determine if we are controlling some extra function
            // that requires special conditions
            if (Functions.Length >  && buttonPressed== "RCA" && CreatedYear > DateTime.Now.Year - )
                return "doSomething";
        }
    }

重构后代码

 public class RemoteControl
    {
        private string[] Functions { get; set; }
        private string Name { get; set; }
        private int CreatedYear { get; set; }

        private bool HasExtraFunctions（string buttonPressed）
        {
            get { return Functions.Length >  && buttonPressed== "RCA" && CreatedYear > DateTime.Now.Year - ; }
        }

        public string PerformCoolFunction(string buttonPressed)
        {
            // Determine if we are controlling some extra function
            // that requires special conditions
            if (HasExtraFunctions（buttonPressed）)
                return "doSomething";
        }
    }