>我有两个单独的文件,第一个是使用第二个(APIService.js(获取不同API的组件(List.js(。要更正抓取,URL 需要接收全局变量。现在,我正在尝试从 APIService 文件中的函数重新定义这些变量,但没有成功。变量在API calls
注释之前以APIService.js
重新定义。
我有两个问题:
- 为什么没有重新定义全局变量
naptanId
? - 是否可以从组件定义和传递这些变量?
伪代码
- 检测信标
- 重新定义纳普坦ID
- 使用最近定义的变量的组件提取 API
- API 调用已完成
- 数据传递回组件
- 设置状态
列表.js
componentDidMount() {
// Executes first function
APIService._fetchStopPoint((resp1) => {
console.log("Stoppoint", resp1)
// ... and set the bus state with the first response
this.setState({
bus: resp1
});
// ... based on the response, convert array to string
const lines = (resp1.lines.map((line) => line.name)).toString()
// ... pass lines to sencond function
APIService._fetchArrivalTimes(lines, (resp2) => {
// .. and set the tube state with the second response
this.setState({
isLoading: false,
tube: resp2
});
});
});
}
APIService.js
// Variables
// ***********************************************************************
let naptanId = undefined
let lines = undefined
let ice = '59333'
let mint = '57011'
let blueberry = '27686'
let nearestBeacon = undefined;
let newBeaconId = undefined;
let setIce = false;
let setBlueberry = false;
let setMint = false;
// Beacon detection
// ***********************************************************************
const region = {
identifier: 'Estimotes',
uuid: '354A97D8-9CAF-0DC7-CE0E-02352EBE90CD',
};
// Request for authorization while the app is open
Beacons.requestWhenInUseAuthorization();
Beacons.startMonitoringForRegion(region);
Beacons.startRangingBeaconsInRegion(region);
Beacons.startUpdatingLocation();
// Listen for beacon changes
const subscription = DeviceEventEmitter.addListener('beaconsDidRange', (data) => {
const ibeacons = data.beacons
// var lowestAccuracySeen = 0.5;
let lowestAccuracySeen = "immediate"
// Check if beacons are updating
if (ibeacons && ibeacons.length > 0) {
// Loop through beacons array
for (var i = 0; i < ibeacons.length ; i++) {
// Find beacons with same minor ...
var foundBeacon = ibeacons.find(function(closestBeacon) {
// ... and return the beacon the lowest accuracy seen
// return closestBeacon.accuracy.toFixed(2) < lowestAccuracySeen;
return closestBeacon.proximity == lowestAccuracySeen
});
// If found ...
if (foundBeacon) {
// ... define the lowest accuracy and the nearest beacon
lowestAccuracySeen = foundBeacon.accuracy;
nearestBeacon = foundBeacon;
// Identify what component to render against nearest beacon
setIce = nearestBeacon.minor == ice ? true : false;
setMint = nearestBeacon.minor == mint ? true : false;
setBlueberry = nearestBeacon.minor == blueberry ? true : false;
if (setIce) {
// THESE VARIABLES CANNOT BE REDEFINED
naptanId = "490004936E"
lines = "55"
} else if (setMint) {
} else if (setBlueberry) {
};
}
}
}
});
// API calls
// ***********************************************************************
class APIService {
// Fecth stop point info
static _fetchStopPoint(cb) {
console.log(naptanId, lines)
fetch(`https://api.tfl.gov.uk/StopPoint/${naptanId}`)
.then(stopData => {
try {
stopData = JSON.parse(stopData._bodyText); // Converts data to a readable format
cb(stopData, naptanId);
} catch(e) {
cb(e);
}
})
.catch(e => cb(e));
}
// Fetch arrival times info
static _fetchArrivalTimes(lines, cb) {
fetch(`https://api.tfl.gov.uk/Line/${lines}/Arrivals/${naptanId}`)
.then(arrivalData => {
try {
arrivalData = JSON.parse(arrivalData._bodyText);
arrivalTime = arrivalData
cb(arrivalData);
} catch(e) {
cb(e);
}
})
.catch(e => cb(e));
}
// Fetch status info
static _fetchStatus(lines) {
fetch(`https://api-argon.digital.tfl.gov.uk/Line/${lines}/Status`)
.then(statusData => {
try {
statusData = JSON.parse(statusData._bodyText); // Converts data to a readable format
cb(statusData);
} catch(e) {
cb(e);
}
})
.catch(e => cb(e));
}
}
module.exports = APIService;
处理这些全局变量(跨不同组件(的最简单方法是使用 AsyncStorage:
let response = await AsyncStorage.getItem('listOfTasks'); //get, in any components
AsyncStorage.setItem('listOfTasks', 'I like to save it.'); //set, in any components
对于性能更关键的全局变量,你也可以考虑 Realm 数据库(如 CoreData,iOS 和 Android 中的 SQLite(。