如何使用云功能和云FireStore维护状态

云功能不能保证按顺序或只发射一次。因此,你必须使它们是等幂的。

您可以通过以下方式解决此问题:

1. 始终使用事务更新状态,这样2个客户机就不会同时尝试更改状态。
2. 创建一个状态表,用于管理状态,并基于当前状态与前一状态运行函数。
3. 客户端不能将状态更改为小于当前存在值的值。

状态.json

[
  {"currentState": "state1", "action": "state2", "newStates": ["state2"]},
  {"currentState": "state1", "action": "state3", "newStates": ["state2", "state3"]},
  {"currentState": "state1", "action": "state4", "newStates": ["state2", "state3", "state4"]},
  {"currentState": "state1", "action": "state5", "newStates": ["state2", "state3", "state4", "state5"]},
  {"currentState": "state2", "action": "state3", "newStates": ["state3"]},
  {"currentState": "state2", "action": "state4", "newStates": ["state3", "state4"]},
  {"currentState": "state2", "action": "state5", "newStates": ["state3", "state4", "state5"]},
  {"currentState": "state3", "action": "state4", "newStates": ["state4"]},
  {"currentState": "state3", "action": "state5", "newStates": ["state4", "state5"]},
  {"currentState": "state4", "action": "state5", "newStates": ["state5"]}
]

应用程序JS

function processStates (beforeState, afterState) {
  const states = require('../states');
  let newStates;

  // Check the states and set the new state
  try {
    newStates = states.filter(function(e) {return e.currentState == beforeState && e.action == afterState;})[0].newStates;
  }
  catch (err) {
    newStates = null;
  }

  console.log(`newStates: ${newStates}`);

  if (newStates) {
    newStates.forEach(newState) {
      // Process state change here
      switch (newState) {
        case 'state1': {
          // Process state1 change
          break;
        }
        case 'state2': {
          // Process state2 change
          break;
        }
        default: {
        }
      }
    }
  }
}

一旦您有了一个状态数组,您就可以使用 forEach 或 map 处理所需的命令。