Skip to main content

MVC - What a view should never contain( part 2)

Part 1
Ieri am promis ca revin cu un post despre ce nu ar trebuii sa contina un view.
Pornim de la o clasa PersonModel care are urmatoarea definitie:
public class PersonModel
{
public string Name { get; set; }
public int Age { get; set; }
public string Address { get; set; }
}
Pentru acest model avem urmatorul view:
@model PersonModel

@{
Layout = null;
}

<!DOCTYPE html>

<html>
<head>
<title>Person</title>
</head>
<body>
<fieldset>
<legend>PersonModel</legend>

<div class="display-label">Name</div>
<div class="display-field">
@Html.DisplayFor(model => model.Name)
</div>

<div class="display-label">Age</div>
<div class="display-field">
@Html.DisplayFor(model => model.Age)
</div>

<div class="display-label">Address</div>
<div class="display-field">
@Html.DisplayFor(model => model.Address)
</div>
</fieldset>
</body>
</html>
Mai tarziu apare o noua cerinta in aplicatie, ca sa se afiseze si coodonatele GPS a locatiei date. Pentru acest lucru se foloseste o adresa web care stie sa rezolve orice adresa. O implementare simpla este urmatoarea:
@model CIC.PersonModel
@{
Layout = null;

string coordLat;
string coordLong;

var request = WebRequest.Create(someAddress + "?location=" + Model.Address);
var webResponse = request.GetResponse();
using (var contentStream = new StreamReader(webResponse.GetResponseStream()))
{
var content = contentStream.ReadToEnd();
webResponse.Close();
string[] coords = content.Split(' ');
coordLong = coords[0];
coordLat = coords[1];
}
}
<!DOCTYPE html>
<html>
<head>
<title>Person</title>
</head>
<body>
<fieldset>
<legend>PersonModel</legend>
<div class="display-label">
Name</div>
<div class="display-field">
@Html.DisplayFor(model => model.Name)
</div>
<div class="display-label">
Age</div>
<div class="display-field">
@Html.DisplayFor(model => model.Age)
</div>
<div class="display-label">
Address</div>
<div class="display-field">
@Html.DisplayFor(model => model.Address)
</div>
<div class="display-label">
GPS Location</div>
<div class="display-field">
@coordLong
@coordLat
</div>
</fieldset>
</body>
</html>
Pagina functioneaza fara nici o problema doar ca in viewul face mult prea multe lucruri. Din el se face un request spre o alta componenta( serviciu), prin intermediul caruia se obtin coordonatele GPS a unei adrese, care se afiseza in view.
Modelul nu contine toate datele necesare pentru a afisa tot ce este necesar. Din aceasta cauza se ajunge sa se faca un apel spre o componenta externa. Nu are importanta daca aceasta componenta este un serviciu extern sau o clasa din assemblyul nostru. Toate datele necesare trebuie sa fie continute de catre model. Orice data trebuie sa ajunga in view prin intermediul modelului.
O solutie este sa adaugam doua propietati in PersonModel care sa reprezinte coordonatele GPS( sau putem sa ne cream o clasa care sa stocheze longitudinea si latitudinea - dar tot ca si o propietate din PersonModel o sa fie).
public class PersonModel
{
public string Name { get; set; }
public int Age { get; set; }
public string Address { get; set; }
public string Longitude { get; set; }
public string Latitude { get; set; }
}
Inițializarea coordonatelor urmeaza sa fie mutata in controler. Problema de la care am pornit a fost rezolvata, insa ... apare un smell la orizont. Nu foarte puternic, dar extrem de periculos. Apelul spre serviciu se face direct din controler, cea ce nu e normal. Da, este adevarat ca controlerul ar trebuii sa pregateasca modelul, dar obtinerea coordonatelor ar trebuii sa se faca in alt loc. De exemlu putem sa scoatem acest apel intr-o alta clasa.

Comments

  1. La capitolul asta - care sunt responsabilitatile controller-ului, programatorii inca au diverse pareri :)
    Ca model-ul e incarcat dintr-un web service, database sau fisier nu e asa important, normalvoi lucra doar cu o interfata injectata in controller, insa unii vor zice:

    - modelul trebuie sa stie sa se incarce singur ("ActiveRecord", mai ales prin lumea Ruby), iar controller-ul sa zica doar model.Load()

    - altii vor zice: nu, ActiveRecord e un anti-pattern, modelul trebuie sa fie cat mai dummy, si alta clasa sa fie responsabila de incarcarea lui ("service", "repository", "context" sau alte nume..) - mai ales prin lumea Java care vad modeul ca un DTO

    - dupa care vor veni altii si vor zice: DTO duce la anemic domain model, care e iarasi un anti pattern, si fie se intorc la prima varianta, fie la o combinatie de domain model + viewmodel..

    Lumea .NET, care a intrat mai tarziu in joc, se ia fie dupa unii fie dupa altii.. :)

    ReplyDelete
  2. Eu prefer ca action-ul din controller sa fie cit mai simplu ... asa ca , probabil, ActiveRecord, nu?

    ReplyDelete
  3. Asa cum spunea si Tudor pareriile sunt impartite. In cazul unui model pentru view eu il prefer cat mai simplu. Daca ar avea forma la ActiveRecord atunci in model pot sa ajunga obiecte sau date de care nu ai nevoie.
    Personal imi place sa trag o linie f. clara si precisa intre obiectele din business layer si cele din UI( model). Chiar daca cele doua coexista impreuna, prefer sa fie diferite, iar modelul sa contina doar datele de care am nevoie in view si atata. Orice camp in plus, care nu e folosit in view nu isi are rostul.

    ReplyDelete
  4. Multi prefera ca modelul sa fie chior (doar proprietati), view-ul chior (doar "lipirea" proprietatile din model pe HTML), controller-ul subtirel (apel servicii colo-colo) si inca un service layer.

    ReplyDelete

Post a Comment

Popular posts from this blog

How to check in AngularJS if a service was register or not

There are cases when you need to check in a service or a controller was register in AngularJS.
For example a valid use case is when you have the same implementation running on multiple application. In this case, you may want to intercept the HTTP provider and add a custom step there. This step don’t needs to run on all the application, only in the one where the service exist and register.
A solution for this case would be to have a flag in the configuration that specify this. In the core you would have an IF that would check the value of this flag.
Another solution is to check if a specific service was register in AngularJS or not. If the service was register that you would execute your own logic.
To check if a service was register or not in AngularJS container you need to call the ‘has’ method of ‘inhector’. It will return TRUE if the service was register.
if ($injector.has('httpInterceptorService')) { $httpProvider.interceptors.push('httpInterceptorService&#…

ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded

Today blog post will be started with the following error when running DB tests on the CI machine:
threw exception: System.InvalidOperationException: The Entity Framework provider type 'System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer' registered in the application config file for the ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded. Make sure that the assembly-qualified name is used and that the assembly is available to the running application. See http://go.microsoft.com/fwlink/?LinkId=260882 for more information. at System.Data.Entity.Infrastructure.DependencyResolution.ProviderServicesFactory.GetInstance(String providerTypeName, String providerInvariantName) This error happened only on the Continuous Integration machine. On the devs machines, everything has fine. The classic problem – on my machine it’s working. The CI has the following configuration:

TeamCity.NET 4.51EF 6.0.2VS2013
It seems that there …

Run native .NET application in Docker (.NET Framework 4.6.2)

Scope
The main scope of this post is to see how we can run a legacy application written in .NET Framework in Docker.

Context
First of all, let’s define what is a legacy application in our context. By a legacy application we understand an application that runs .NET Framework 3.5 or higher in a production environment where we don’t have any more the people or documentation that would help us to understand what is happening behind the scene.
In this scenarios, you might want to migrate the current solution from a standard environment to Docker. There are many advantages for such a migration, like:

Continuous DeploymentTestingIsolationSecurity at container levelVersioning ControlEnvironment Standardization
Until now, we didn’t had the possibility to run a .NET application in Docker. With .NET Core, there was support for .NET Core in Docker, but migration from a full .NET framework to .NET Core can be costly and even impossible. Not only because of lack of features, but also because once you…