如何调用从CouchDB检索到的文档的函数？

I am using Cradle to store objects in CouchDB from my Node.js server. The objects contain functions....

我正在使用Cradle从我的Node.js服务器在CouchDB中存储对象。对象包含函数....

function AnObject(a, b){
this.a = a; this.b = b;
this.addparts = function(){return this.a + this.b;};}

var cradle = require('cradle');
var db = new(cradle.Connection)('http://localhost', 5984, {cache: true, raw: false}).database('myDB');

var myObject = new AnObject(1, 2);
console.log("addparts:" + myObject.addparts());
db.save('myObjectId', myObject);

This works fine and the document is stored but when I retrieve it, I can no longer call the function on the returned document...

这工作正常，文档存储但是当我检索它时，我不能再在返回的文档上调用该函数...

db.get('myObjectId', function(err, myRetrievedObject){
console.log("addparts:" + myRetrievedObject.addparts());
});

This fails with a (Property is not a function) Error..

这失败了（属性不是函数）错误..

node cradle_test

cradle_test.js:21
console.log("addparts:" + myRetrievedObject.addparts());
                                         ^
TypeError: Property 'addparts' of object {"_id":"myObjectId","_rev":"2-83535db5101fedfe30a1548fa2641f29","a":1,"b":2,"addparts":"function (){return this.a + this.b;}"} is not a function

2 个解决方案

#1

CouchDB stores JSON. Functions are not valid JSON. Functions are never stored in the database.

CouchDB存储JSON。函数无效JSON。函数永远不会存储在数据库中。

I recommend you move the functions out into a prototype.

我建议你将这些功能移到原型中。

function AnObject(a, b){
    this.a = a; this.b = b;
}

AnObject.prototype.addparts = function(){
    return this.a + this.b;
};

db.get('myObjectId', function(err, myRetrievedObject){
    var obj = Object.create(AnObject.prototype);
    // for some value of extend ( https://github.com/Raynos/pd#pd.extend )
    extend(obj, myRetrievedObject);
    console.log("addparts:" + obj.addparts());
});

This way your not saving functions and you can still operate on your object using your methods. You just have to make sure that your retrieved object is made an instance of AnObject

这样您的保存功能就可以使用您的方法对您的对象进行操作。您只需确保将检索到的对象作为AnObject的实例

#2

There is a way to store functions in CouchDB: as attachments.

有一种方法可以在CouchDB中存储函数：作为附件。

Define your functions in a separate .js file (for example, a set of functions you want to share across multiple servers or app instances).

在单独的.js文件中定义函数（例如，要在多个服务器或应用程序实例之间共享的一组函数）。

/modules/db.js:

/modules/db.js：

var db = {}

db.insert = function(nanoDb, object, cb){
  //insert new doc
  nanoDb.insert(object, function(err, body, header) {
    if (!err) {
      cb.call(null, {success: true, data: body});

    }else{
      console.log('[insert] ', err.message); 
      cb.call(null, {success: false, error: err.message});
    }
  });
}

db.bulkInsert = function(nanoDb, array, cb){
  //structure for bulk insert
  var data = {
    docs: array
  }
  //insert new doc
  nanoDb.bulk(data, function(err, body, header) {
    if (!err) {
      cb.call(null, {success: true, data: body});

    }else{
      console.log('[bulkInsert] ', err.message); 
      cb.call(null, {success: false, error: err.message});
    }
  });
}

db.bulkDelete = function(nanoDb, array, cb){
  for(i in array){
    array[i]._deleted = true;
  }
  var data = {
    docs: array
  }
  //check if the url exists in the db
  nanoDb.bulk(data, function(err, body) {
    if (!err){  
      cb.call(null, {success: true, data: data});
    }else{
      console.log('[bulkDelete] ', err.message);
      cb.call(null, {success: false, error: err.message});
    }
  });
}

db.view = function(nanoDb, design, view, params, cb){
  nanoDb.view(design, view, params, function(err, body) {
    if (!err){
      var docs = util.extractDocs(body);
      cb.call(null, {success: true, data: docs});
    }else{
      console.log('[view] ', err.message);
      cb.call(null, {success: false, error: err.message});
    }
  });
}

db.search = function(nanoDb, design, index, params, cb){
  nanoDb.search(design, index, params, function(err, body) {
    if (!err) {
      var docs = util.extractDocsSearch(body);
      cb.call(null, {success: true, data: docs});
    }else{
      console.log('[search] ', err.message);
      cb.call(null, {success: false, error: err.message});
    }
  }); 
}

db.follow = function(nanoDb, params){
  var feed = nanoDb.follow(params);
  return feed;
}

module.exports = db;

Use a CouchApp to deploy the functions as attachments (in a design doc):

使用CouchApp将功能部署为附件（在设计文档中）：

//your couchapp
var couchapp = require('couchapp')

//url to your database
var url = '...';

//empty design doc (for attachments)
ddoc = {
  _id: '_design/mods'
};

//folder containing .js files
couchapp.loadAttachments(ddoc, './modules/');

//this function uploads your attachments
couchapp.createApp(ddoc, url, function(app) {
  app.push(function(){
    //do something
  });
});

Now, get the functions wherever you need them:

现在，在任何需要的地方获取功能：

//use mikaels request module if you like
var request = require('request');

//tell the app where to get your .js file
//sometimes a good idea to persist these references in memory or even in your couchdb
var fileUrl = '/_design/modules/db.js'

//set this variable in the proper scope
var db;

//we'll use this to 'require' the .js file
var _require = function(src, file) {
  var m = new module.constructor();
  m.paths = module.paths;
  m._compile(src, file);
  return m.exports;
}

request({ url: fileUrl, json: true }, function (err, response, data) {
  if (!err && response.statusCode === 200) {
    //now we assign our required .js file (object w/functions) back into usable form
    //woot woot!
    db = _require(data);
  }else{
    console.log('[request]', err);
  }
});

Do stuff!

做东西！

db.doSomething()

#1