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你什么时候在 C/C++/C# 等中使用代码块？我知道它们背后的理论原因，但是你什么时候在实际程序中使用它们呢？

编辑：我刚刚意识到我在switch语句中使用它们，否则变量将在同一范围内（grr 用于类似的东西i）：

switch (x) { case "abc": { /* code */ } break; }

等（为了澄清，在 switch 语句中，不需要额外的大括号。）

有关的：

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4 回答 4

10

I sometimes, but rarely, use naked code blocks to limit scope. For example, take the following code:

double bedroomTemperature = ReadTemperature(Room.Bedroom);
database.Store(Room.Bedroom, bedroomTemperature);

double bathroomTemperature = ReadTemperature(Room.Bathroom);
database.Store(Room.Bedroom, bedroomTemperature);

The code looks fine at first glance, but contains a subtle copy-pasta error. In the database we have stored the bedroom temperature for both readings. If it had been written as:

{
    double bedroomTemperature = ReadTemperature(Room.Bedroom);
    database.Store(Room.Bedroom, bedroomTemperature);
}

{
    double bathroomTemperature = ReadTemperature(Room.Bathroom);
    database.Store(Room.Bedroom, bedroomTemperature);
}

Then the compiler (or even IDE if it is intelligent enough) would have spotted this.

However, 90% of the time the code can be refactored to make the naked blocks unnecessary, e.g. the above code would be better written as a loop or two calls to a method that reads and stores the temperature:

foreach (Room room in [] { Room.Bedroom, Room.Bathroom })
{
    double temperature = ReadTemperature(room);
    database.Store(room, temperature);
}

Naked blocks are useful on occasion though.

于 2009-03-27T17:59:35.317 回答
3

我对开关块做同样的事情，即使它不是必需的。一般来说，我使用代码块，它们要么使代码更具可读性（无论是通过为相似的代码块提供相似的外观还是仅仅获得缩进），或者它们正确地作用域变量。

于 2009-03-27T17:32:22.217 回答
1

finally您可以通过使用代码块和 RAII 对象在 C++中获得类似的行为。

{
   std::fstream f(filename)
   ...
}

无论是什么导致我们离开块，都会在析构函数中释放文件描述符。

（就我个人而言，我仍在努力实践这一点。我的 c 根牢牢地抓住了我的习惯......）

于 2009-03-27T17:31:03.983 回答
0

除了显而易见的（“当语法需要时”，例如在 switch 或 try catch finally 中）之外，
每当您需要将 2 个或更多语句的块视为一个原子单元时

于 2009-03-27T17:31:07.210 回答