5.2.3 From Object-Oriented Designs to API’s

• APIs (Application Programming Interfaces) are outlines of classes.
  • They show the declarations of the features of the classes
  • They hide the definitions of the features of the classes
• An API lists
  • The fields availble for recording information
  • The methods available for manipulating information

  class watch {    int hour, minute, second;      public:    void set( int hr, int min, int sec);    void tick( );    void display( );  };

  Class name: watch Fields: hours, minutes, seconds Methods: $\bullet$ advance the time by one second $\bullet$ set the watch to a requested time $\bullet$ display the watch time Constructors: default mechanisms

• The names of arguments are optional within the declaration of methods

  class car {    double max, current, rate;      public:    void fill();    void fill( double gallons );    void drive( doubles );  };

  Class name: car Fields: $\bullet$ tank size $\bullet$ gas amount $\bullet$ miles per galon Methods: $\bullet$ fill tank $\bullet$ fill a specified number of gallons $\bullet$ drive a specified distance Constructors: default mechanisms

• The APIs allow to seperate issues of class usages from issues of class implementations
• Applications can get access only to features idetified to be ‘public’