kandi X-RAY | Design Summary
kandi X-RAY | Design Summary
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QUESTION
I was making a simple to do app with mvc pattern and I saw an article which said you shouldn't pass the model values directly to the view, which made the project more complex than I thought (I am relatively new to programming and this is the first time I am trying out a design pattern).
But then later on I talked to someone who said that that is not true and you can send the model data directly to view, he didn't even use classes or some kind of grouping to separate the function he just put them in separate files.
I was wondering if there is a guideline that I couldn't find or we can do whatever we want as long as they are kind of separated. I would love an article or a guide to read up on as well.
...ANSWER
Answered 2021-Jun-16 at 01:01Since, I am not 100% sure the context in which you are trying to apply the MVC pattern, a good generic explanation of MVC can be found in GoF's 1995 book, Design Patterns: Elements of Reusable Object Oriented Software.
In the book, they state the following.
The Model is the application object, the View is its screen presentation, and the Controller defines the way the user interface reacts to user input.
A more robust explanation can be found from Martin Fowler where he also makes the case for a variation of Model View Controller that uses a Presentation Model.
If you are referring to Spring MVC then there is some magic that blurs the lines a bit. But in general, you have a controller that represents some screen or an encapsulated piece of functionality that the user (web requests) interact with. The controller serves up responses that are derived from the domain, usually via a Spring Service (i.e. @Service). The domain (Model) doesn't know anything about the View and the View may or may not know anything about the domain.
Given that, the View should be derived from the Model. But that's not always the case since sometimes how we present things to a screen is not the best logical way to model things in our domain - not to mention, the domain should be presentation agnostic. This leads into Fowler's argument for a Presentation Model, which is a model that belongs to the Presentation.
I call this a Presentation Model because it's a model that is really designed for and thus part of the presentation layer.
Microsoft took that idea and ran with it in a variant of MVC called MVVM (Model View ViewModel).
You can read more about that in Microsoft's documentation on ASP.Net Core.
So, back to your original question of "Should you pass the model directly to the view?" If you are using MVC then the controller is what provides the interaction. But if you're really asking, "Can you bind your view directly to the model?" If your model has all the stuff you need organized how your view needs it, then sure. And if it's simple enough, maybe that's the way to go. Otherwise, you could go with something like a Presentation Model or MVVM.
QUESTION
I'm a student learning about database design and currently learning about the relationships of - one-to-one, one-to-many, many-to-many. I understand the concept well enough, but feel like I'm lacking experience/information on how it would be implemented in a real production scenario.
My question is this
If I have a blog website with a Blog Post as an entity and comments for each blog post, how would you handle the comments in the database?`
Would you use a one-to-many relationship and just store all the comments in a single table. Then link those comments to each blog post and user who created it?
What if each comment had a sub-comment? Would you create a separate table for sub-comments and link it to a single comment? Would that cause too much overhead and confusion within the DB itself?
I get the concepts and all, but don't understand best practices for handling what seems like basic stuff.
Thanks in advance!
...ANSWER
Answered 2021-Jun-15 at 16:06The simplest solution is to stick with a one-to-many relationship. Use one table and store one comment per row, with references to the post and the comment author, and a timestamp so you can sort the comments chronologically.
You seem uncertain about whether you need a "threaded comment" hierarchy. This is more complex, so if you don't need it, don't bother.
If you do need to show comment threads, then you should learn about running recursive queries in MySQL 8.0: https://dev.mysql.com/doc/refman/8.0/en/with.html#common-table-expressions-recursive
You still only need one table. Don't create a second table for sub-comments. Just store comments like in your one-to-many example, but each comment may link to its "parent" comment when it is a reply.
Another solution that many sites use is to skip implementing their own comment system, and just embed a comment service like Disqus. That's likely to be much more reliable and safe than yours. But if you're doing this as a learning exercise, that's worthwhile too.
QUESTION
the swiftui code below should apply the sephia.tone filter to the current photo, to do it I used the code below but the filter is not applied, can anyone explain to me where the problem is? when I click on sepia I make the call to the function that applies the CiFilter,what is this due to? because the filter is not applied correctly
Swift UI Code:
...ANSWER
Answered 2021-Jun-15 at 16:15You need to set input image for the filter and take care of the interoperately between Image and UImage
QUESTION
I read this answer, which clarified a lot of things, but I'm still confused about how I should go about designing my primary key.
First off I want to clarify the idea of WCUs. I get that WCU is the write capacity of max 1kb per second. Does it mean that if writing a piece of data takes 0.25 seconds, I would need 4 of those to be billed 1 WCU? Or each time I write something it consumes 1 WCU, but I could also write X times within 1 second and still be billed 1 WCU?
Usage
I want to create a table that stores the form data for a set of gyms (95% will be waivers, the rest will be incidents reports). Most of the time, each forms will be accessed directly via its unique ID. I also want to query the forms by date, form, userId, etc..
We can assume an average of 50k forms per gym
Options
First option is straight forward: having the formId be the partition key. What I don't like about this option is that scan operations will always filter out 90% of the data (i.e. the forms from other gyms), which isn't good for RCUs.
Second option is that I would make the gymId the partition key, and add a sort key for the date, formId, userId. To implement this option I would need to know more about the implications of having 50k records on one partition key.
Third option is to have one table per gyms and have the formId as partition key. This seems to be like the best option for now, but I don't really like the idea of having a a large number of tables doing the same thing in my account.
Is there another option? Which one of the three is better?
Edit: I'm assuming another option would be SimpleDB?
...ANSWER
Answered 2021-May-21 at 20:26For your PK design. What data does the app have when a user is going to look for a form? Does it have the GymID, userID, and formID? If so, make a compound key out of that for the PK perhaps? So your PK might look like:
QUESTION
I have a given, unmodifiable table design which resembles:
...ANSWER
Answered 2021-Jun-15 at 15:17One hacky solution would switch the sign of the second column:
QUESTION
looking to understand the order in which kubenetes examine the pods using the 3 type of probes- startup, readiness and live.
How to understand or design these 3 probes correctly for normal applications? What is the chance of getting conflict or breaking the application if the startup probe has wrong entries
...ANSWER
Answered 2021-Jun-15 at 16:06This runs first. When it succeeds, the Readiness Probe and Liveness Probe are run continuously. If this fails, the container is killed.
Use this for "slow staring apps", you can use the same command as Liveness if you want.
The kubelet uses startup probes to know when a container application has started. If such a probe is configured, it disables liveness and readiness checks until it succeeds, making sure those probes don't interfere with the application startup. This can be used to adopt liveness checks on slow starting containers, avoiding them getting killed by the kubelet before they are up and running.
From configuring probes
Liveness probeThis is used to kill the container, in case of a deadlock in the application.
Readiness probeThis is used to check that the container can receive traffic.
QUESTION
I'm trying to display data from firebase in an antd table using hooks. I created a mini version of this application with a simple bootstrap design pulling the data from firebase with:
...ANSWER
Answered 2021-Jun-15 at 14:46I have the dumb and answered my own question. I did not in fact try every variation with/without .columns.
QUESTION
Iam new to RN and currently developing a project. I need to create a highlighting for a view like this like [the 1st image],[this is the design i have right now],[code for the template]. The template is then used in the renderitem prop to render the view. Please have a look through this?. Also this highlighting should be given only to the respective box when it is clicked.
...ANSWER
Answered 2021-Jun-15 at 12:45You can use Conditional (ternary) operator to change the border color.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Conditional_Operator
QUESTION
I am modeling a Time-constrained CVRP. The problem is to minimize the total travel time (not including the package dropping time) subject to vehicle (delivery) capacity and total time spent (per vehicle) constraints. The package dropping time refers to an additional time to be spent at each node, and the total time spent equals to the travel time plus this additional time. I have the below model that works for a single vehicle-type case. I would like to introduce two-vehicle type concept in there, meaning that I have a set of V1 type vehicles and another set of V2 type vehicles. The only difference of the vehicle-types is the per time cost of travel. Let x denote the per time unit cost of travel by V1, and y denote the per time unit travel cost of V2. How can I design the model so that it incorporates this additional aspect?
ANSWER
Answered 2021-Jun-13 at 13:34Simply register two transits callbacks (i.e. one per vehicle type)
Then use the overload of AddDimension() to pass an array of registered transit callback index.
QUESTION
I'm writing an app in WPF, trying to use the MVVM-design pattern (which is new to me).
I have a DataGrid bound to an ObservableCollection.
Delete the currently selected DataGrid-row using a 'Delete'-button. I've tried a plethora of forum-posts and videos to find a solution. The solution has probably stared me right in the face several times, but at this point I'm more confused than I was when I first started.
Any assistance would be appreciated.
ViewModel (updated with working code, thanks to EldHasp):
...ANSWER
Answered 2021-Jun-14 at 20:15You can use Prism. Intall package Prism.Core then Install-Package Microsoft.Xaml.Behaviors.Wpf -Version 1.1.31 packages in your project, in your xaml declare namespace as - xmlns:i="http://schemas.microsoft.com/xaml/behaviors"
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Install Design
You can use Design like any standard Java library. Please include the the jar files in your classpath. You can also use any IDE and you can run and debug the Design component as you would do with any other Java program. Best practice is to use a build tool that supports dependency management such as Maven or Gradle. For Maven installation, please refer maven.apache.org. For Gradle installation, please refer gradle.org .
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