PouchDB从对象数组中发出对象 [英] PouchDB emit object from an array of objects

问题描述

我想搜索一个对象数组（封装在一个大对象中），并只发出一个内部对象。因此，假设我在PouchDB中插入了一个JSON，如下所示：

I would like to search trough an array of objects (that are encapsulated in one big object), and emit only the one of the internal objects. So let's suppose I have a JSON inserted into PouchDB that is looks like this:

{ 
 "_id": "5eaa6d20-2019-44e9-8aba-88cfaf8e02542",
 "data" = [
  {
    "id": 1452,
    "language": "java"
  },
  {
    "id": 18787453,
    "language": "javascript"
  },
  {
    "id": 145389721,
    "language": "perl"
  }]
}

如何在搜索id = 145389721的语言时让PouchDB返回以下结果：

How to get PouchDB to return the following result when searching for a language with an id = 145389721:

  {
    "id": 145389721,
    "language": "perl"
  }

谢谢！

推荐答案

在上面的场景中，最简单的方法是使用typescript，写一个临时查询：

In the scenario above the easiest way, using typescript, is to write a temp query:

        db.query((doc, emit) => {
          for (let element of doc.data) {
            if (element.id === 145389721) {
              emit(element);
            }
          }
        }).then((result) => {
          for (let row of result.rows) {
            console.log(row.key);
          }
        })

使用永久查询它看起来像这样：

Using permanent queries it would have looked like this:

let index = {
  _id: '_design/my_index',
  views: {
    "by_id": {
      "map": "function(doc) {for (let element of doc.data) {emit(element.id, element); }}"
    }
  }
};

// save it
this.db.put(index).catch(error => {
  console.log('Error while inserting index', error);
});

//query it 
this.db.query('my_index/by_id', { startkey: 145389721, endkey: 145389721}).then(result => {
  for (let row of result.rows) {
    console.log(row.value);
  }
}).catch(error => {
  console.log('Error while querying the database with an index', error);
});

这篇关于PouchDB从对象数组中发出对象的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！