如何对从CouchDB检索到的文档调用函数？
如何对从CouchDB检索到的文档调用函数？
提问于 2012-01-26 20:36:34
我正在使用Cradle从我的Node.js服务器将对象存储在CouchDB中。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);这可以很好地工作，并且文档被存储，但是当我检索它时，我不能再对返回的文档调用函数了……
db.get('myObjectId', function(err, myRetrievedObject){
console.log("addparts:" + myRetrievedObject.addparts());
});此操作失败，并显示(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回答 2
Stack Overflow用户
回答已采纳
发布于 2012-01-26 22:54:18
CouchDB存储JSON。函数不是有效的JSON。函数永远不会存储在数据库中。
我建议您将函数移出到原型中。
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());
});这样你就不会保存函数，而且你仍然可以使用你的方法来操作你的对象。您只需确保检索到的对象是AnObject的一个实例
Stack Overflow用户
发布于 2014-05-04 16:57:03
有一种方法可以在CouchDB中存储函数：as attachments。
在单独的.js文件中定义您的函数(例如，您希望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：
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;使用CouchApp将函数部署为附件(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
});
});现在，在您需要的任何地方获取函数：
//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);
}
});做点什么吧！
db.doSomething()页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/9018193
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