Enumeration classes and magic values

1. Advantages of enumerating classes

1.1 Readability

stay idea Under the environment of , Move the mouse pointer up to see the corresponding comments

1.2 Parameter passing error

For example, in some important configurations such as ： Message queuing switch 、 queue ; The cache key; wait . Enumerating classes can prevent you from writing a key attribute wrong .

1.3Switch Sentence advantage

If one in the business Switch There may be many situations in , There may be cross-border problems . Use enumeration values , You can prevent cross-border problems before compiling

1.4 It is convenient to check where it has been used

stay idea In the environment , direct Ctrl+Shift+F Search the enumeration value , You can find out where this business attribute is used . If it is magic value , Can't find it

2. The harm of magic value

• ditto 1.4, If it is magic value , It cannot be associated with other related businesses
• You may write wrong words
• Maybe the same business , Different people , In different situations , The value is different from the business mapping relationship
• Out of sight idea notes

3. Misunderstanding of using enumeration classes

3.1 Business understanding deviation

I found such a problem in my daily work ： For delete_flag Field ,1 For normal ,0 Represents the deletion of .
But many places use Enale.YES.getvalue() and Enable.NO.getvalue(). This is obviously not directly related to this business
The correct usage should be to build a DeleteFlag Enumeration class , use USING(1) and FORBIDDEN(0) To indicate whether to delete

3.2 The essence is the enumeration value of magic value

For example, there is such an enumeration class ：NUMBER, The attributes inside are ONE(1) TWO(2) THREE(3), Such enumeration is essentially a magic value , He has no direct connection with the meaning of business

3.3 Not for enum Separate subcontracting

All related businesses enum It should be put under the same bag . Otherwise, there may be situations where you want to find enumeration classes of related businesses but cannot find them

3.4 Regardless of business , all enum Under the same bag

All of the different modules enum If you put it under the same bag , It is also difficult to distinguish intuitively . It should be based on the degree of business coupling , Fine molecular package under the package , Store related enumeration classes