cpp实现的一个状态机

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状态机

用cpp实现一个简单的状态机

StateMachine.h

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#pragma once
#include <unordered_map>

using StateType = int;
static StateType NullState = -1;

class StateMachine;
class State;

class State {
public:
  virtual ~State(){};

  virtual void OnStateEnter(StateMachine *stateMachine) = 0;
  virtual void OnTick(StateMachine *stateMachine, int64_t TimeNow) = 0;
  virtual void OnStateExit(StateMachine *stateMachine) = 0;
};

class StateMachine {
private:
  // 该状态机下的所有状态
  std::unordered_map<StateType, State *> allStates;
  // 该状态机当前状态
  StateType curState = NullState;

public:
  StateMachine() = default;
  ~StateMachine() {
    for (auto &stateIter : allStates) {
      if (stateIter.second != nullptr) {
        stateIter.second = nullptr;
        delete stateIter.second;
      }
    }
  }

  // 注册新的状态到状态机
  bool RegisterState(StateType type, State *statePtr);

  // 状态转移
  bool Trans(StateType newState);

  // TICK函数
  void Tick(int64_t TimeNow);

  StateType GetState() { return curState; }
};

#define CREATE_STATE(name)                                                     \
  class name##State;                                                           \
  using name##StatePtr = std::unique_ptr<name##State>;                         \
  class name##State : public State {                                           \
  public:                                                                      \
    virtual void OnStateEnter(StateMachine *stateMachine) override;            \
    virtual void OnTick(StateMachine *stateMachine, int64_t TimeNow) override; \
    virtual void OnStateExit(StateMachine *stateMachine) override;             \
  };

StateMachine.cc

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#include "StateMachine.h"

// 注册新的状态到状态机
bool StateMachine::RegisterState(StateType type, State *statePtr) {
  std::unordered_map<StateType, State *>::iterator iter = allStates.find(type);
  if (iter != allStates.end()) {
    return false;
  }

  allStates.insert({type, std::forward<State *>(statePtr)});
  return true;
}

// 状态转移
bool StateMachine::Trans(StateType newState) {
  // 当前状态退出
  if (curState != NullState) {
    std::unordered_map<StateType, State *>::iterator iter =
        allStates.find(curState);
    if (iter != allStates.end() && iter->second != nullptr) {
      iter->second->OnStateExit(this);
    }
  }

  // 下一状态进入
  auto iter = allStates.find(newState);
  if (iter == allStates.end()) {
    curState = NullState;
    return false;
  }
  if (iter->second != nullptr) {
    curState = newState;
    iter->second->OnStateEnter(this);
  }

  return true;
}

// TICK函数
void StateMachine::Tick(int64_t TimeNow) {
  if (curState == NullState) {
    return;
  }

  std::unordered_map<StateType, State *>::iterator curStateIter =
      allStates.find(curState);
  if (curStateIter != allStates.end() && curStateIter->second != nullptr) {
    curStateIter->second->OnTick(this, TimeNow);
  }
}