代码改变世界

Google Style 学习

2014-12-27  本文已影响177人  CapJon

头文件

作用域

类

#define DISALLOW_COPY_AND_ASSIGN(TypeName) \\
            TypeName(const TypeName&); \\
            void operator=(const TypeName&)
         private:
        DISALLOW_COPY_AND_ASSIGN(Foo);

其他 C++ 特性

cout << this;   // Prints the address
 cout << *this;  // Prints the contents

命名约定

 int num_errors;                  // Good.
 int num_completed_connections;   // Good

 int error_count;  // Good
 int error_cnt;    // Bad

注释

 bool success = CalculateSomething(interesting_value,
                                   10,     // Default base value.
                                   false,  // Not the first time we're calling this.
                                   NULL);  // No callback.

或使用常量或描述性变量:

 const int kDefaultBaseValue = 10;
 const bool kFirstTimeCalling = false;
 Callback *null_callback = NULL;
 bool success = CalculateSomething(interesting_value,
                                   kDefaultBaseValue,
                                   kFirstTimeCalling,
                                   null_callback);

DoSomething();                  // Comment here so the comments line up.
DoSomethingElseThatIsLonger();  // Comment here so there are two spaces between
                                // the code and the comment.
{ // One space before comment when opening a new scope is allowed,
  // thus the comment lines up with the following comments and code.
  DoSomethingElse();  // Two spaces before line comments normally.
}

// TODO(kl@gmail.com): Use a "*" here for concatenation operator.
// TODO(Zeke) change this to use relations.

如果加 TODO 是为了在 “将来某一天做某事”, 可以附上一个非常明确的时间 “Fix by November 2005”), 或者一个明确的事项 (“Remove this code when all clients can handle XML responses.”)。

格式

ReturnType ClassName::FunctionName(Type par_name1, Type par_name2) {
    DoSomething();
    ...
}

如果同一行文本太多, 放不下所有参数:

ReturnType ClassName::ReallyLongFunctionName(Type par_name1,
                                             Type par_name2,
                                             Type par_name3) {
    DoSomething();
    ...
}

甚至连第一个参数都放不下:

ReturnType LongClassName::ReallyReallyReallyLongFunctionName(
        Type par_name1,  // 4 space indent
        Type par_name2,
        Type par_name3) {
    DoSomething();  // 2 space indent
    ...
}

// Everything in this function signature fits on a single line
ReturnType FunctionName(Type par) const {
  ...
}

// This function signature requires multiple lines, but
// the const keyword is on the line with the last parameter.
ReturnType ReallyLongFunctionName(Type par1,
                                  Type par2) const {
  ...
}

// Comment out unused named parameters in definitions.
void Circle::Rotate(double /*radians*/) {}

bool retval = DoSomething(argument1, argument2, argument3);

如果同一行放不下, 可断为多行, 后面每一行都和第一个实参对齐, 左圆括号后和右圆括号前不要留空格:

bool retval = DoSomething(averyveryveryverylongargument1,
                          argument2, argument3);

如果函数参数很多, 出于可读性的考虑可以在每行只放一个参数:

bool retval = DoSomething(argument1,
                          argument2,
                          argument3,
                          argument4);

如果函数名非常长, 以至于超过 行最大长度, 可以将所有参数独立成行:

if (...) {
  ...
  ...
  if (...) {
    DoSomethingThatRequiresALongFunctionName(
        very_long_argument1,  // 4 space indent
        argument2,
        argument3,
        argument4);
  }

switch (var) {
  case 0: {  // 2 space indent
    ...      // 4 space indent
    break;
  }
  case 1: {
    ...
    break;
  }
  default: {
    assert(false);
  }
}

while (condition) {
  // Repeat test until it returns false.
}
for (int i = 0; i < kSomeNumber; ++i) {}  // Good - empty body.
while (condition) continue;  // Good - continue indicates no logic.
Warning
while (condition);  // Bad - looks like part of do/while loop.

if (this_one_thing > this_other_thing &&
    a_third_thing == a_fourth_thing &&
    yet_another & last_one) {
  ...
}

// Good - directives at beginning of line
  if (lopsided_score) {
#if DISASTER_PENDING      // Correct -- Starts at beginning of line
    DropEverything();
#endif
    BackToNormal();
  }

结束语

参考阅读

Google C++ 风格指南 - 中文版
Google 开源项目风格指南

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