如何在ionic 2中使用lokijs-cordova-fs-adapter

Question

我正尝试在我的ionic 2应用程序中使用lokijs。我可以使用lokijs.js。当我试图坚持使用适配器时，我无法坚持下去。可以使用lokijs-cordova-fs-adapter。但当我在我的应用程序中引用它时，如下所示:收到一个无法定位的错误。

var LokiCordovaFSAdapter = require("./cordova-file-system-adapter");

尝试将其添加到我的index.html中，并尝试在ts文件中创建适配器，如下所示：

var adapter = new LokiCordovaFSAdapter({"prefix": "loki"});

在这种情况下获取语法错误。有没有人能举例说明如何使用它？

Answer 1

Ciao，这在离子2上有效，所以一步一步地(我在service中做了这个)：

1. 检查是否同时安装了两个依赖项：

npm install lokijs --save npm install loki-cordova-fs-

• --save

lokijs声明并导入以下内容(在类声明之前)：

声明var require: any；var loki = require('lokijs')；var LokiCordovaFSAdapter =require(“loki-cordova-fs-LokiCordovaFSAdapter”)；var LokiCordovaFSAdapter= new prefix({“prefix”：“loki”})；

• 在服务类中使用以下内容：

db: any；// LokiJS数据库pandas: any；//我们数据库的文档集合对象构造函数(){ console.log("* inicializando...")；this.db = new loki('pandas.db'，{ autoload: true，autoloadCallback: function() { console.log("* database loaded...") }，autosave: true，autosaveInterval: 10 * 1000，//每10秒适配器:适配器})；}

• 使用它(此代码也在服务类中)：

load() { let collection =this.db.getCollection( 'Panda‘)；if (集合== null) { this.pandas =this.db.addCollection(’Panda‘)；} else { this.pandas = collection；}} pandaKamasutra() { console.log("*保存熊猫...“)；for (let i=0；I< 100；i++) this.pandas.insert({ name：’Panda‘+ (i+1)，surename："Whurgh”+I })；} showPandas() { var results = this.pandas.find({})；for (let R of results) console.log(% id: ${r.$loki}, Panda: ${r.name})；}

我花了一个下午来解决这个问题，在浏览了LokiJS和lokijs-cordova-fs-adapter代码之后，我在离子文档here中找到了“亮点”。

希望它也适用于你。=]

Answer 2

请参阅我在https://github.com/cosmith/loki-cordova-fs-adapter/issues/15上的帖子，了解如何在Ionic2中做到这一点(在这里转载)。

我终于在一个Ionic2应用程序中运行了这个(带有typescript)。请务必安装插件cordova-plugin-file。然后像使用Ionic2中的普通提供程序一样使用底部的适配器(我将其安装在我的项目中的/src/lib/loki-cordova-fs-adapter中，名为index.ts)。

有关用法，请参见以下示例：

import { Injectable } from '@angular/core'
import { Platform } from 'ionic-angular'
import * as Loki from 'lokijs'
import * as LokiIndexedAdapter from 'lokijs/src/loki-indexed-adapter'
import { LokiCordovaFSAdapter } from 'lib/loki-cordova-fs-adapter'

const DATABASE_NAME: string = 'yourFilename.db.json'

@Injectable()
export class DatabaseProvider {

  private lokiOptions: any = {
    verbose: true,
    autosave: true,
    autosaveInterval: 60000,
    autoload: true
  }
  private db: any

  public constructor (private platform: Platform, private mobileAdapter: LokiCordovaFSAdapter) {}

  public load (successCallback: any): void {
    if (this.db) {
      successCallback()
    } else {
      this.db = this.loadDatabase(DATABASE_NAME, successCallback)
    }
  }

  private loadDatabase (databaseName: string, successCallback: any): any {
    this.lokiOptions.autoloadCallback = successCallback
    if (this.platform.is('cordova')) {
      this.lokiOptions.adapter = this.mobileAdapter
    } else {
      this.lokiOptions.adapter = new LokiIndexedAdapter()
    }
    return new Loki(databaseName, this.lokiOptions)
  }
}

下面是适配器：

import { Injectable } from '@angular/core'
class LokiCordovaFSAdapterError extends Error {}

// const TAG: string = '[LokiCordovaFSAdapter]'
declare var window: any
declare var cordova: any

@Injectable()
export class LokiCordovaFSAdapter {
  private options: any

  public constructor () {
    this.options = {'prefix': 'loki'}
  }

  public saveDatabase (dbname: string, dbstring: string, callback: any): any {
    // console.log(TAG, 'saving database')
    this._getFile(dbname,
      (fileEntry) => {
        fileEntry.createWriter(
          (fileWriter) => {
            fileWriter.onwriteend = () => {
              if (fileWriter.length === 0) {
                const blob: any = this._createBlob(dbstring, 'text/plain')
                fileWriter.write(blob)
                callback()
              }
            }
            fileWriter.truncate(0)

          },
          (err) => {
            // console.log(TAG, 'error writing file', err)
            throw new LokiCordovaFSAdapterError('Unable to write file' + JSON.stringify(err))
          }
        )
      },
      (err) => {
        // console.log(TAG, 'error getting file', err)
        throw new LokiCordovaFSAdapterError('Unable to get file' + JSON.stringify(err))
      }
    )
  }

  public loadDatabase (dbname: string, callback: any): void {
    // console.log(TAG, 'loading database')
    this._getFile(dbname,
      (fileEntry) => {
        // console.log('got database file')
        fileEntry.file((file) => {
          const reader: FileReader = new FileReader()
          reader.onloadend = (event: any) => {
            const contents: any = event.target.result
            if (contents.length === 0) {
              // console.log(TAG, 'database is empty')
              callback(null)
            } else {
              // console.log('sending back database')
              callback(contents)
            }
          }
          reader.readAsText(file)
        }, (err) => {
          // console.log(TAG, 'error reading file', err)
          callback(new LokiCordovaFSAdapterError('Unable to read file' + err.message))
        })
      },
      (err) => {
        // console.log(TAG, 'error getting file', err)
        callback(new LokiCordovaFSAdapterError('Unable to get file: ' + err.message))
      }
    )
  }

  public deleteDatabase (dbname: string, callback: any): void {
    window.resolveLocalFileSystemURL(cordova.file.dataDirectory,
      (dir) => {
        const fileName: string = this.options.prefix + '__' + dbname
        dir.getFile(fileName, { create: true },
          (fileEntry) => {
            fileEntry.remove(
              () => {
                callback()
              },
              (err) => {
                // console.log(TAG, 'error delete file', err)
                throw new LokiCordovaFSAdapterError('Unable delete file' + JSON.stringify(err))
              }
            )
          },
          (err) => {
            // console.log(TAG, 'error delete database', err)
            throw new LokiCordovaFSAdapterError(
              'Unable delete database' + JSON.stringify(err)
            )
          }
        )
      },
      (err) => {
        throw new LokiCordovaFSAdapterError(
          'Unable to resolve local file system URL' + JSON.stringify(err)
        )
      }
    )
  }

  private _getFile (name: string, handleSuccess: any, handleError: any): void {
    // console.log(TAG, 'Retrieving file: ' + name)
    window.resolveLocalFileSystemURL(cordova.file.dataDirectory,
      (dir) => {
        const fileName: string = this.options.prefix + '__' + name
        dir.getFile(fileName, { create: true }, handleSuccess, handleError)
      },
      (err) => {
        throw new LokiCordovaFSAdapterError(
          'Unable to resolve local file system URL' + JSON.stringify(err)
        )
      }
    )
  }

  // adapted from http://stackoverflow.com/questions/15293694/blob-constructor-browser-compatibility
  private _createBlob (data: string, datatype: string): any {
    let blob: any

    try {
      blob = new Blob([data], { type: datatype })
    } catch (err) {
      window.BlobBuilder = window.BlobBuilder ||
        window.WebKitBlobBuilder ||
        window.MozBlobBuilder ||
        window.MSBlobBuilder

      if (err.name === 'TypeError' && window.BlobBuilder) {
        const bb: MSBlobBuilder = new window.BlobBuilder()
        bb.append(data)
        blob = bb.getBlob(datatype)
      } else if (err.name === 'InvalidStateError') {
        // InvalidStateError (tested on FF13 WinXP)
        blob = new Blob([data], { type: datatype })
      } else {
        // We're screwed, blob constructor unsupported entirely
        throw new LokiCordovaFSAdapterError(
          'Unable to create blob' + JSON.stringify(err)
        )
      }
    }
    return blob
  }
}