Static Members

Static members belong to the class itself instead of one object.
static member A static member is shared by every object of the class.
                            ticketCount
                            ticketCount = 3 (default)ticketCount = 1ticketCount = 4
                        

                            static_members.cpp
                        
Replay: real traced execution (multi-file project)

                            #include <iostream>

class Ticket {
private:
    static int nextId;
    int id;

public:
    Ticket() {
        id = nextId;
        nextId++;
    }

    int number() {
        return id;
    }

    static int nextNumber() {
        return nextId;
    }
};

int Ticket::nextId = 100;

int main() {
    int ticketCount = 3;
    int lastNumber = 0;

    for (int i = 0; i < ticketCount; i++) {
        Ticket ticket;
        lastNumber = ticket.number();
    }

    std::cout << "ticketCount=" << ticketCount << std::endl;
    std::cout << "lastNumber=" << lastNumber << std::endl;
    std::cout << "nextNumber=" << Ticket::nextNumber() << std::endl;
    return 0;
}
#include <iostream>

class Ticket {
private:
    static int nextId;
    int id;

public:
    Ticket() {
        id = nextId;
        nextId++;
    }

    int number() {
        return id;
    }

    static int nextNumber() {
        return nextId;
    }
};

int Ticket::nextId = 100;

int main() {
    int ticketCount = 1;
    int lastNumber = 0;

    for (int i = 0; i < ticketCount; i++) {
        Ticket ticket;
        lastNumber = ticket.number();
    }

    std::cout << "ticketCount=" << ticketCount << std::endl;
    std::cout << "lastNumber=" << lastNumber << std::endl;
    std::cout << "nextNumber=" << Ticket::nextNumber() << std::endl;
    return 0;
}
#include <iostream>

class Ticket {
private:
    static int nextId;
    int id;

public:
    Ticket() {
        id = nextId;
        nextId++;
    }

    int number() {
        return id;
    }

    static int nextNumber() {
        return nextId;
    }
};

int Ticket::nextId = 100;

int main() {
    int ticketCount = 4;
    int lastNumber = 0;

    for (int i = 0; i < ticketCount; i++) {
        Ticket ticket;
        lastNumber = ticket.number();
    }

    std::cout << "ticketCount=" << ticketCount << std::endl;
    std::cout << "lastNumber=" << lastNumber << std::endl;
    std::cout << "nextNumber=" << Ticket::nextNumber() << std::endl;
    return 0;
}

                        
1ticketCount ← 3, lastNumber ← 0⋯25int main() {26    int ticketCount→ 3 = 3; //@ticketCount=1, 427    int lastNumber→ 0 = 0;⋯
2for (int i = 0; i < ticketCount; i++)pass 1 of 3⋯29for (int i0 = 0; i < ticketCount3; i++) {30    Ticket ticket;31    lastNumber = ticket.number();⋯All 3 passes — pass 1 is the card abovepassi
10
21
32
3id ← 100, nextId ← 101pass 1 of 3⋯8public:9    Ticket() {10        id→ 100 = nextId100;11        nextId→ 101++;12    }⋯All 3 passes — pass 1 is the card abovepassidnextId
1163840 → 100100 → 101
2100 → 101101 → 102
3101 → 102102 → 103
4ticket ← (empty)⋯29for (int i = 0; i < ticketCount; i++) {30    Ticket ticket→ (empty);31    lastNumber0 = ticket(empty).number();32}⋯
5int number()pass 1 of 3⋯14int number() {15    return id100;16}⋯All 3 passes — pass 1 is the card abovepassid
1100
2101
3102
6lastNumber ← 100⋯30    Ticket ticket;31    lastNumber→ 100 = ticket(empty).number();32}⋯
7ticket ← (empty)⋯29for (int i = 0; i < ticketCount; i++) {30    Ticket ticket→ (empty);31    lastNumber100 = ticket(empty).number();32}⋯
8lastNumber ← 101⋯30    Ticket ticket;31    lastNumber→ 101 = ticket(empty).number();32}⋯
9ticket ← (empty)⋯29for (int i = 0; i < ticketCount; i++) {30    Ticket ticket→ (empty);31    lastNumber101 = ticket(empty).number();32}⋯
10lastNumber ← 102⋯30    Ticket ticket;31    lastNumber→ 102 = ticket(empty).number();32}⋯
11std::cout << "ticketCount=" << ticketCount << std::endl;⋯34std::cout << "ticketCount=" << ticketCount3 << std::endl;35std::cout << "lastNumber=" << lastNumber102 << std::endl;36std::cout << "nextNumber=" << Ticket::nextNumber() << std::endl;37return 0;⋯outputticketCount=3
lastNumber=102
12static int nextNumber()⋯18static int nextNumber() {19    return nextId103;20}⋯
13std::cout << "nextNumber=" << Ticket::nextNumber() << std::endl;⋯35    std::cout << "lastNumber=" << lastNumber << std::endl;36    std::cout << "nextNumber=" << Ticket::nextNumber() << std::endl;37    return 0;38}⋯outputnextNumber=103
1ticketCount ← 1, lastNumber ← 0⋯25int main() {26    int ticketCount→ 1 = 1;27    int lastNumber→ 0 = 0;⋯
2for (int i = 0; i < ticketCount; i++)⋯29for (int i0 = 0; i < ticketCount1; i++) {30    Ticket ticket;31    lastNumber = ticket.number();⋯
3id ← 100, nextId ← 101⋯8public:9    Ticket() {10        id→ 100 = nextId100;11        nextId→ 101++;12    }⋯
4ticket ← (empty)⋯29for (int i = 0; i < ticketCount; i++) {30    Ticket ticket→ (empty);31    lastNumber0 = ticket(empty).number();32}⋯
5int number()⋯14int number() {15    return id100;16}⋯
6lastNumber ← 100⋯30    Ticket ticket;31    lastNumber→ 100 = ticket(empty).number();32}⋯
7std::cout << "ticketCount=" << ticketCount << std::endl;⋯34std::cout << "ticketCount=" << ticketCount1 << std::endl;35std::cout << "lastNumber=" << lastNumber100 << std::endl;36std::cout << "nextNumber=" << Ticket::nextNumber() << std::endl;37return 0;⋯outputticketCount=1
lastNumber=100
8static int nextNumber()⋯18static int nextNumber() {19    return nextId101;20}⋯
9std::cout << "nextNumber=" << Ticket::nextNumber() << std::endl;⋯35    std::cout << "lastNumber=" << lastNumber << std::endl;36    std::cout << "nextNumber=" << Ticket::nextNumber() << std::endl;37    return 0;38}⋯outputnextNumber=101
1ticketCount ← 4, lastNumber ← 0⋯25int main() {26    int ticketCount→ 4 = 4;27    int lastNumber→ 0 = 0;⋯
2for (int i = 0; i < ticketCount; i++)pass 1 of 4⋯29for (int i0 = 0; i < ticketCount4; i++) {30    Ticket ticket;31    lastNumber = ticket.number();⋯All 4 passes — pass 1 is the card abovepassi
10
21
32
43
3id ← 100, nextId ← 101pass 1 of 4⋯8public:9    Ticket() {10        id→ 100 = nextId100;11        nextId→ 101++;12    }⋯All 4 passes — pass 1 is the card abovepassidnextId
1163840 → 100100 → 101
2100 → 101101 → 102
3101 → 102102 → 103
4102 → 103103 → 104
4ticket ← (empty)⋯29for (int i = 0; i < ticketCount; i++) {30    Ticket ticket→ (empty);31    lastNumber0 = ticket(empty).number();32}⋯
5int number()pass 1 of 4⋯14int number() {15    return id100;16}⋯All 4 passes — pass 1 is the card abovepassid
1100
2101
3102
4103
6lastNumber ← 100⋯30    Ticket ticket;31    lastNumber→ 100 = ticket(empty).number();32}⋯
7ticket ← (empty)⋯29for (int i = 0; i < ticketCount; i++) {30    Ticket ticket→ (empty);31    lastNumber100 = ticket(empty).number();32}⋯
8lastNumber ← 101⋯30    Ticket ticket;31    lastNumber→ 101 = ticket(empty).number();32}⋯
9ticket ← (empty)⋯29for (int i = 0; i < ticketCount; i++) {30    Ticket ticket→ (empty);31    lastNumber101 = ticket(empty).number();32}⋯
10lastNumber ← 102⋯30    Ticket ticket;31    lastNumber→ 102 = ticket(empty).number();32}⋯
11ticket ← (empty)⋯29for (int i = 0; i < ticketCount; i++) {30    Ticket ticket→ (empty);31    lastNumber102 = ticket(empty).number();32}⋯
12lastNumber ← 103⋯30    Ticket ticket;31    lastNumber→ 103 = ticket(empty).number();32}⋯
13std::cout << "ticketCount=" << ticketCount << std::endl;⋯34std::cout << "ticketCount=" << ticketCount4 << std::endl;35std::cout << "lastNumber=" << lastNumber103 << std::endl;36std::cout << "nextNumber=" << Ticket::nextNumber() << std::endl;37return 0;⋯outputticketCount=4
lastNumber=103
14static int nextNumber()⋯18static int nextNumber() {19    return nextId104;20}⋯
15std::cout << "nextNumber=" << Ticket::nextNumber() << std::endl;⋯35    std::cout << "lastNumber=" << lastNumber << std::endl;36    std::cout << "nextNumber=" << Ticket::nextNumber() << std::endl;37    return 0;38}⋯outputnextNumber=104
pass	`id`	`nextId`
1	163840 → 100	100 → 101
2	100 → 101	101 → 102
3	101 → 102	102 → 103
All 3 passes — pass 1 is the card above
pass	`i`
1	0
2	1
3	2
All 4 passes — pass 1 is the card above
pass	`i`
1	0
2	1
3	2
4	3