Question

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The Definitive C++ Book Guide and List

i have a lot of questions about declaration and implementation, according to most (books, tutorials, blog entries) a class declaration with constructor, methods and member functions:

class Book
{
public:
    Book(const string & author_,
         const string & title_,
         const string & publisher_,
         double price_,
         double weight_);
    string getName()
    {
        string name;
        name = author + ": " + title;
        return name.substr(0, 40);
    }
    double getPrice();
    double getWeight();
private:
    string author, title, publisher;
    double price, weight;
};

i understand all the the access level, the Constructor, reference operator (pointer too!), the pointer operator, but when I read things less trivial like:

class Type
{
public:
    enum TypeT {stringT, intT, doubleT, unknownT};

    // 1. which means "explicit"?
    // 2. what's ": typeId(typeId_)"? after the Ctor declaration
    explicit Type(TypeT typeId_) : typeId(typeId_) {}

    // 3. "const" after the declaration which means?
    BaseValue * newValue() const
    {
        return prototypes[typeId]->clone();
    }

    TypeT getType() const
    {
        return typeId;
    }

    static void init();
    {
        prototypes[stringT] = new Value<string>("");
        prototypes[intT] = new Value<int>(0);
        prototypes[doubleT] = new Value<double>(0);
    }

private:
    TypeT typeId;

    static vector<BaseValue *> prototypes;
};

I feel lost and really have not found clear information about the above points.

Addition to answering my question, if you know somewhere where they have these “tricks” of language

Answer 1

A good introductory book to C++ should answer your questions.

1. explicit means the constructor must be mentioned explicitely in the code, the type cannot be constructed automatically from another type when required.
2. Member initialization. The class member is not constructed with its default constructor, but rather the arguments given here.
3. The method can be called on a const object.