ES.22: Don't declare a variable until you have a value to initialize it with
ES.22:没有合适的初始值就不要定义变量
Reason(原因)
Readability. Limit the scope in which a variable can be used. Don't risk used-before-set. Initialization is often more efficient than assignment.
可读性。限制变量可用的范围。不要冒设定前使用的风险。初始化通常比赋值更高效。
Example, bad(反面示例)
Example, bad(反面示例)
This would be fine if there was a default initialization for SomeLargeType that wasn't too expensive. Otherwise, a programmer might very well wonder if every possible path through the maze of conditions has been covered. If not, we have a "use before set" bug. This is a maintenance trap.
如果SomeLargeType存在一个代价不高的默认初始化,这段代码问题不大。否则,程序员可能特别想知道是否通过条件迷宫的所有路径都被覆盖了。如果不是,我们就遇到了一个设定前使用的错误。这是一个维护陷阱。
For initializers of moderate complexity, including for const variables, consider using a lambda to express the initializer; see ES.28.
对于中等复杂度初始化器,包括常量,考虑使用lambda表达式实现。参见ES.28
Enforcement(实施建议)
- Flag declarations with default initialization that are assigned to before they are first read.
- 标记包含默认初始化操作却在第一次使用之前赋值的情况。
- Flag any complicated computation after an uninitialized variable and before its use.
- 标记任何定义了未初始化变量又在它被使用之前进行了复杂处理的qi
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