Node.js 如何在MongoDB 2.4中从数组内部的文档中删除属性

在MongoDB 2.4中使用本机Nodejs驱动程序，并尝试从数组中嵌入的文档中删除属性。例如，如何从

grades

数组中嵌入的所有文档中删除

gym

属性，其中

gym

是

562e7c1ae6c3e8ce29abfe05

？因此：

{
    "_id" : ObjectId("562abaaffb5870b8fb9dca3f"),
    "grades" : [
        {
            "_id" : ObjectId("562e7bbe70ee82bb290192bd"),
            "discipline" : "55aae5b7848b9c8bf4ecbb5c",
            "grade" : "55aae5b7848b9c8bf4ecbb4c",
            "gym" : "562e7c1ae6c3e8ce29abfe06",
            "registeredOn" : ISODate("2015-10-26T19:15:10.565Z")
        },
        {
            "discipline" : "55aae5b7848b9c8bf4ecbb5c",
            "grade" : "55aae5b7848b9c8bf4ecbb4d",
            "gym" : "562e7c1ae6c3e8ce29abfe05",
            "registeredOn" : ISODate("2015-10-26T19:17:08.603Z"),
            "_id" : ObjectId("562e7c34e6c3e8ce29abfe06")
        },
        {
            "discipline" : "55aae5b7848b9c8bf4ecbb5c",
            "grade" : "55aae5b7848b9c8bf4ecbb4d",
            "gym" : "562e7c1ae6c3e8ce29abfe05",
            "registeredOn" : ISODate("2015-10-26T19:17:08.603Z"),
            "_id" : ObjectId("562e7c34e6c3e8ce29abfe07")
        }
    ],
},
{
    "_id" : ObjectId("562abaaffb5870b8fb9dca3f"),
    "grades" : [
        {
            "_id" : ObjectId("562e7bbe70ee82bb290192bd"),
            "discipline" : "55aae5b7848b9c8bf4ecbb5c",
            "grade" : "55aae5b7848b9c8bf4ecbb4c",
            "gym" : "562e7c1ae6c3e8ce29abfe07",
            "registeredOn" : ISODate("2015-10-26T19:15:10.565Z")
        },
        {
            "discipline" : "55aae5b7848b9c8bf4ecbb5c",
            "grade" : "55aae5b7848b9c8bf4ecbb4d",
            "gym" : "562e7c1ae6c3e8ce29abfe05",
            "registeredOn" : ISODate("2015-10-26T19:17:08.603Z"),
            "_id" : ObjectId("562e7c34e6c3e8ce29abfe06")
        }
    ],
}

我需要这个：

{
    "_id" : ObjectId("562abaaffb5870b8fb9dca3f"),
    "grades" : [
        {
            "_id" : ObjectId("562e7bbe70ee82bb290192bd"),
            "discipline" : "55aae5b7848b9c8bf4ecbb5c",
            "grade" : "55aae5b7848b9c8bf4ecbb4c",
            "gym" : "562e7c1ae6c3e8ce29abfe06",
            "registeredOn" : ISODate("2015-10-26T19:15:10.565Z")
        },
        {
            "discipline" : "55aae5b7848b9c8bf4ecbb5c",
            "grade" : "55aae5b7848b9c8bf4ecbb4d",
            "registeredOn" : ISODate("2015-10-26T19:17:08.603Z"),
            "_id" : ObjectId("562e7c34e6c3e8ce29abfe06")
        },
        {
            "discipline" : "55aae5b7848b9c8bf4ecbb5c",
            "grade" : "55aae5b7848b9c8bf4ecbb4d",
            "registeredOn" : ISODate("2015-10-26T19:17:08.603Z"),
            "_id" : ObjectId("562e7c34e6c3e8ce29abfe07")
        }
    ],
},
{
    "_id" : ObjectId("562abaaffb5870b8fb9dca3f"),
    "grades" : [
        {
            "_id" : ObjectId("562e7bbe70ee82bb290192bd"),
            "discipline" : "55aae5b7848b9c8bf4ecbb5c",
            "grade" : "55aae5b7848b9c8bf4ecbb4c",
            "gym" : "562e7c1ae6c3e8ce29abfe07",
            "registeredOn" : ISODate("2015-10-26T19:15:10.565Z")
        },
        {
            "discipline" : "55aae5b7848b9c8bf4ecbb5c",
            "grade" : "55aae5b7848b9c8bf4ecbb4d",
            "registeredOn" : ISODate("2015-10-26T19:17:08.603Z"),
            "_id" : ObjectId("562e7c34e6c3e8ce29abfe06")
        }
    ],
}

下面的查询将仅删除指定id为I的第一个匹配文档。但是，第二份文档带有

“_id”：ObjectId（“562e7c34e6c3e8ce29abfe07”）

仍将具有健身房属性

562e7c1ae6c3e8ce29abfe05

multi

似乎是多余的，那么有没有办法删除所有id为I的健身房属性

collections.users.update({
    "grades.gym": "562e7c1ae6c3e8ce29abfe05"
}, {
    $unset: {
        "grades.$.gym": "562e7c1ae6c3e8ce29abfe05"

    }
}, {
    multi: true
})

最好使用返回光标，使用方法对其进行迭代，以访问集合中符合条件的每个文档，从而获得数组字段，删除符合条件的属性并更新文档，如下所示：

collection.find({ "grades.gym": "562e7c1ae6c3e8ce29abfe05" }).each(function(err, doc){
    // handle err
    var new_grades = doc.grades.map(function (grade){ 
        if (grade.gym == "562e7c1ae6c3e8ce29abfe05") { delete grade.gym; }
        return grade;
    });

    collection.update({ "_id": doc._id },{ "$set": { "grades": new_grades }});
});