Question

我正在尝试在我的离子2应用程序中使用lokijs。我可以使用lokijs.js。当试图坚持使用适配器我不能。我准备好了lokijs-cordova-fs-adapter可以使用。但是当我在我的应用程序中引用它时如下所示：得到一个无法找到它的错误。

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

尝试在我的index.html中添加它并尝试在我的ts文件中创建适配器，如下所示：

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

在这种情况下出现语法错误。有人可以举例说明如何使用它吗？

Answer 1

Ciao，这适用于Ionic 2，所以一步一步（我在service内做了这个）：

检查是否已安装两个依赖项：

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

声明并导入以下内容（在类声明之前）：

declare var require: any;
var loki = require('lokijs');
var LokiCordovaFSAdapter = require("loki-cordova-fs-adapter");
var adapter = new LokiCordovaFSAdapter({"prefix": "loki"});

在服务类中使用以下内容：

db: any; // LokiJS database
pandas: any; // our DB's document collection object

constructor() {
  console.log("* inicializando...");

  this.db = new loki('pandas.db', {
    autoload: true,
    autoloadCallback: function() {
      console.log("* database loaded...")
    },
    autosave: true,
    autosaveInterval: 10 * 1000, //every 10 seconds
    adapter: adapter
  });
}

使用它（此代码也在服务类中）：

load() {
  let collection = this.db.getCollection('pandas');
  if (collection == null) {
    this.pandas = this.db.addCollection('pandas');
  } else {
    this.pandas = collection;
  }
}

pandaKamasutra() {
  console.log("* Save the pandas...");
  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}`);
}

我今天下午解决了这个问题，在游过LokiJS和lokijs-cordova-fs适配器代码后，我在Ionic文档here中找到了'light'。

希望它也适合你。 =]

Answer 2

请参阅https://github.com/cosmith/loki-cordova-fs-adapter/issues/15上的帖子，了解如何在Ionic2中执行此操作（此处重新发布）。

我终于在Ionic2应用程序（带有打字稿）中运行了这个程序。请务必安装插件cordova-plugin-file。然后使用底部的适配器，就像Ionic2中的普通Provider一样（我已将它安装在我项目的/src/lib/loki-cordova-fs-adapter中 - 命名为index.ts）。

对于使用，这是一个例子：

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)
  }
}

这是适配器：

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
  }
}

如何在离子2中使用lokijs-cordova-fs-adapter

2 个答案: