Interfaces

Questions 1 to 5 of 6

1. 1. The print_report function in Example 1 takes a TemperatureSource. What does it need from that interface?

   The sensor's class name, so it can print itA method that returns one number, read_celsiusEvery method the sensor has, so it can pick one at run timeA write method, so it can store each reading
2. 2. The BrokenSensor example names its method read_celcius, but the base method is read_celsius. What does the override word do here?

   It makes read_celcius a second virtual function that runs next to the base methodIt hides the base method and compiles without any messageIt makes the class concrete, so an object of it can be createdIt asks the compiler to check that the method replaces a base method, so the typo becomes an error
3. 3. Match each interface term with its meaning.

   Choose the matching item for each row.

   pure virtual functionChoose…many methods, where most callers use only one or two of thema new method that hides the base one, so the class stays abstractmakes deleting an object through the interface pointer clean up the whole objecta method ending in `= 0` with no body, so each class must write its own versionvirtual destructorChoose…many methods, where most callers use only one or two of thema new method that hides the base one, so the class stays abstractmakes deleting an object through the interface pointer clean up the whole objecta method ending in `= 0` with no body, so each class must write its own versionfat interfaceChoose…many methods, where most callers use only one or two of thema new method that hides the base one, so the class stays abstractmakes deleting an object through the interface pointer clean up the whole objecta method ending in `= 0` with no body, so each class must write its own versionconst-less overrideChoose…many methods, where most callers use only one or two of thema new method that hides the base one, so the class stays abstractmakes deleting an object through the interface pointer clean up the whole objecta method ending in `= 0` with no body, so each class must write its own version
4. 4. Statement: when you design an interface, start from the full list of methods on the object you already have, and copy all of them into the interface.

   False, because the interface should be shaped by what callers do, so you start from the caller and include only the methods they useTrue, because a complete copy of the object's methods makes the interface safe for future callers
5. 5. In Example 3, count_lines takes only a LineReader&, not a LineWriter&. Why?

   Readers run faster than writers, so only readers are allowed in loopsThe compiler accepts only one interface per parameterIt only reads, so its signature accepts nothing that can write, and a write call inside it would not compileA LineBuffer cannot be passed as a LineReader