解析：查询包含的指针

Question

我有一个“产品”集合，它具有指向我在产品查询中包含的“类别”集合的指针引用。如何查询此类别值，而无需单独查询类别本身？

var productQuery = new Parse.Query("Product"); 
productQuery.include("category"); 

if(params.category) { 
    productQuery.equalTo("category", params.category); 
} 

... 

productQuery.find({ 
    success: function(products) {...}, 
    error: function(err) {...} 
}); 

什么不想：

var productQuery = new Parse.Query("Product"); 
productQuery.include("category"); 

if(params.category) { 
    var categoryQuery = new Parse.Query("Category"); 
    categoryQuery.equalTo("name", params.category); 
    categoryQuery.first({ 
     success: function(foundCategory) { 
      productQuery.equalTo("category", foundCategory); 
     } 
    }); 

    // Yes, I am aware that in this example the product query below would likely be executed before the category query above finishes. 
} 

... 

productQuery.find({ 
    success: function(products) {...}, 
    error: function(err) {...} 
}); 

Answer 1

什么你要找的是一个Parse.Query的matchesQuery或matchesKeyInQuery方法：http://parseplatform.org/Parse-SDK-JS/api/classes/Parse.Query.html#methods_matchesQuery

它会基本上尽你所能做的事情，除非更有效率，并且在您编写的高级代码上更干净。