C++ 初始化和赋值的不同

int a = 12; // initialization, copy 0X000C to a
a = 12; // assignment, copy 0X000C to a

class String {
  public:
    String( const char *init ); // intentionally not explicit!
    ~String();
    String( const String &that );
    String &operator =( const String &that );
    String &operator =( const char *str );
    void swap( String &that );
    friend const String // concatenate
        operator +( const String &, const String & );
    friend bool operator <( const String &, const String & );
    //...
  private:
    String( const char *, const char * ); // computational
    char *s_;
};

初始化的构造过程比较简单：先分配一个足够大的空间然后填充上数据：

String::String( const char *init ) {
    if( !init ) init = "";
    s_ = new char[ strlen(init)+1 ];
    strcpy( s_, init );
}

析构过程更简单：

看来在条件允许的情况下最好在初始化的时候就赋值，而尽量避免用=号赋值了。


相关链接：	C++ Common Knowledge: Assignment and Initialization Are Different

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