Backbone.js调用city.save()报错：需指定url属性或函数，请求排查

Hey there! Let's break down why you're hitting this Backbone.js error when calling city.save() and how to fix it.

• Model缺少URL配置：Your CityModel is an empty extension of Backbone.Model with no url property or url() method defined. When you call save() on a Backbone Model, it needs to know exactly where to send the update request. The url you set on CityCollection only applies to collection-level operations (like fetching all items or creating a new item via the collection)—it doesn't automatically apply to individual model saves.
• Request header异常关联：Since Backbone can't determine a valid target URL for the save request, it fails early in the request initialization process, which leads to the strange request header issues you're seeing (like invalid or missing headers that Backbone would normally set automatically).

1. Add URL configuration to your CityModel
   There are two standard ways to do this, depending on your API's REST structure:
   • Fixed URL (for simple cases)：If your API uses the same endpoint for creating and updating city resources:

     var CityModel = Backbone.Model.extend({
       url: "/api/epermit"
     });
     

   • Dynamic URL (RESTful best practice)：If your API expects updates to go to a resource-specific URL (like /api/epermit/:id), use a function to generate the URL dynamically:

     var CityModel = Backbone.Model.extend({
       url: function() {
         var baseUrl = "/api/epermit";
         // Use collection URL for new models, resource URL for existing ones
         return this.isNew() ? baseUrl : `${baseUrl}/${encodeURIComponent(this.id)}`;
       }
     });
     

2. Verify API endpoint matching
   Double-check that your backend API supports:
   • POST requests to /api/epermit for creating new cities
   • PUT/PATCH requests to /api/epermit/:id for updating existing cities
     Adjust the model's url if your API uses a different pattern.
3. Validate model instantiation
   Make sure you're creating your city model correctly before calling save(), especially if it's an existing resource that needs an ID:

   // Example: Instantiate a model with an ID for updates
   var city = new CityModel({ id: 123, name: "Shanghai" });
   // Call save with updates and error handling
   city.save({ name: "Updated Shanghai" }, {
     success: (model, res) => console.log("Save successful!", res),
     error: (model, res) => console.log("Save failed:", res)
   });
   

4. Troubleshoot request headers
   Once the model has a valid URL, Backbone will automatically set standard headers like Content-Type: application/json. If you still see header issues, you can manually specify headers in the save options:

   city.save({}, {
     headers: {
       "Content-Type": "application/json",
       // Add any custom headers your API requires here
     }
   });
   

内容的提问来源于stack exchange，提问作者user9101605