动态链接查询

Question

有任何方法可以动态链接查询吗？

例如，给定以下GET请求

/collection?field1=value1&field2=value2&sort=field3 asc

没有排序查询是很容易的

/collection?field1=value1&field2=value2

var query = {}
for (var key in query) {
    query[key] = req.query[key]
}

Collection.find(query)

但是，如果有可选的查询键，例如排序、展开和选择分别到Collection.sort、Collection.populate、Collection.select的映射，那么如何构建GET请求？

换句话说，假设您有一个查询方法的动态数组：

queries = [populate, select, sort]

解决办法是否如下：

var query = Collection.find()
for (var q in queries)
    query = query.q

Answer 1

您只需迭代查询参数，并分离出操作和实际查询条件的参数。用你的例子：

​

// sample data for req.query
const req = {
  query: {
    sort: "field9",
    field1: "someValue",
    field2: "otherValue",
    field3: "highValue"
  }
};

const queries = new Map();
const operations = new Map([
    ["populate", false], 
    ["sort", false], 
    ["select", false]
]);
for (const [key, value] of Object.entries(req.query)) {
    if (operations.has(key)) {
        operations.set(key, value);
    } else {
        queries.set(key, value);
    }
}

// here:
//    queries contain the non-operation pairs
//    operations (if not false) contain the operation value such
//      as sort => "field9"

console.log("operations:");
for (let [key, value] of operations.entries()) {
   console.log(`${key} => ${value}`);
}
console.log("queries:");
for (let [key, value] of queries.entries()) {
   console.log(`${key} => ${value}`);
}

​

要运行该操作，您必须检查存在哪些操作，并根据存在哪些操作来分支代码和查询。