En este artículo os presentaremos a los servicios también conocidos como “services”. Una de las piezas fundamentales en el desarrollo de aplicaciones Angular.
¿Qué son los servicios?
Un servicio es la capa encargada de traer/proporcionarnos los datos a nuestra aplicación de Angular.
Normalmente, nuestro servicio para acceder a estos datos suelen conectarse al servidor donde están almacenada dicha información, por ejemplo una BBDD, una API Rest, etc.
Además de proporcionarnos dichos datos, un servicio también mantiene la lógica de acceso a dichos datos, es decir, define que podemos hacer y que no con los datos de la fuente, define a que datos podemos acceder, como realizaremos las llamadas a dichos datos, etc.
Los servicios nos van a permitir desde comunicar componentes hasta consumir webservices o cualquier otra tarea.
Los servicios se encargan en traer datos y los componentes en presentarlos de manera correcta.
Creando nuestro primer servicio manualmente
Para crear nuestros servicios vamos al directorio src>app y creamos un nuevo fichero:
Como casi todo en Angular, los servicios son clases TypeScript.
La estructura de su nombre debe de ser nombreServicio.service.ts
Ahora, en su interior definimos la clase y realizamos el export para que sea visible desde el resto del modulo:
Un ejemplo podría de un servicio (que por el momento no se comunica con nadie) y con los datos hardcodeados podría ser:
Si queremos podemos hacer una representación “más real” (aunque también hardcodeada ya que no nos estamos conectado a ningún sitio ni obteniendo dichos datos desde algún medio) del servicio haciendo que getUsuarios nos devuelva un listado de objetos de los usuarios de una BBDD (por ejemplo):
Hasta ahora, simplemente hemos mostrando los datos por la consola pero ni los hemos guardado en nuestro componente y hemos trabajado con ellos.
Pero podemos guardar los datos en nuestro componente además, una vez tenemos los datos en nuestro componente podemos mostrar dicha información en nuestro template de la siguiente manera:
El resultado será:
Creando nuestro un servicio mediante a la instrucción de @angular/cli
Existe la alternativa de agilizar la velocidad de creación de la estructura de servicio gracias a la instrucción @angular/cli:
ng generate service <name> [options]
ng g s <name> [options]
En el fichero del servicio, vemos que además nos aparece un @Inyectable del que hablaremos en próximos artículos.
Si nos fijamos esta alternativa de crear un servicio es mucho más rápida y además nos crea un archivo para escribir los test de dicho servicio.
Tight Coupling vs Dependency Injection
En el ejemplo que acabamos de mostrar, realizábamos una instanciación del servicio users.service.ts mediante a una llamada a su constructor (que aunque no existe sería por defecto en blanco) new UserService() y posteriormente realizábamos la llamada hacía su método getUsers.
Pero ¿Qué pasaría si queremos pasarle parámetros a dicho constructor? Pues que tendremos que escribir dichos parámetros en cada uno de los componentes o no mostrará un mensaje de error:
Podemos añadir las claves al constructor cuando realizamos la instanciación de la clase y resolvemos el problema:
Pero como podéis ver tenemos una dependencia de la clase UserService que contiene el servicio. Por lo que, nuestro componente no va a actuar de forma independiente al servicio esto es lo que se conoce bajo el termino de Tight Coupling.
Para resolver esta dependencia, en la próxima lección os explicaremos como resolver esto mediante a la inyección de dependencias (injection dependency).
Espero que os haya gustado la lección. Nos vemos, un saludo 🙂
28 agosto, 2021 a las 3:13
I have been browsing online more than three hours as of late, but I by no means discovered any
interesting article like yours. It is lovely price sufficient for me.
Personally, if all site owners and bloggers made
excellent content material as you did, the web might be much more helpful than ever before.
29 agosto, 2021 a las 21:04
My programmer is trying to convince me to move to .net from PHP.
I have always disliked the idea because of the costs.
But he’s tryiong none the less. I’ve been using Movable-type on a variety of websites for about a year and am anxious about
switching to another platform. I have heard excellent
things about blogengine.net. Is there a way I can import all my wordpress content into it?
Any kind of help would be really appreciated!
19 octubre, 2021 a las 19:38
Howdy! I realize this is kind of off-topic however I needed to ask.
Does building a well-established website such as yours require a massive amount work?
I’m brand new to writing a blog but I do write in my journal daily.
I’d like to start a blog so I will be able to share my experience and thoughts online.
Please let me know if you have any recommendations or tips for new aspiring bloggers.
Appreciate it!
21 octubre, 2021 a las 23:27
Hey! I’m at work browsing your blog from my new iphone
4! Just wanted to say I love reading your blog and look forward to all your posts!
Keep up the excellent work!
Review my page: http://www.comegnolaw.com
21 octubre, 2021 a las 23:50
Very good information. Lucky me I found your blog by accident (stumbleupon).
I have saved it for later!
Also visit my blog post: chef’s knife
22 octubre, 2021 a las 0:45
Just what I was searching for, appreciate it for posting.
Here is my web site: tooth pain relief
22 octubre, 2021 a las 2:35
Hi there Dear, are you actually visiting this website
regularly, if so afterward you will definitely obtain fastidious know-how.
22 octubre, 2021 a las 4:23
Fantastic blog you have here but I was wondering if you knew of
any community forums that cover the same topics discussed here?
I’d really like to be a part of group where I can get suggestions from
other experienced individuals that share the same interest.
If you have any recommendations, please let me know.
Cheers!
22 octubre, 2021 a las 5:10
We stumbled over here from a different page and thought I may as well check
things out. I like what I see so now i’m following you. Look forward to looking over your web
page yet again.
22 octubre, 2021 a las 7:53
This blog was… how do you say it? Relevant!!
Finally I have found something which helped
me. Many thanks!
22 octubre, 2021 a las 8:31
But wanna remark that you have a very nice website, I the style it really stands out.
Feel free to visit my web site; https://tanhua666.com/home.php?mod=space&uid=950169&do=profile&from=space
22 octubre, 2021 a las 8:50
Can I simply just say what a relief to uncover someone
that truly knows what they are discussing on the
net. You actually understand how to bring a problem to light and make it
important. A lot more people should read this and understand this side of the story.
I can’t believe you are not more popular because you
definitely possess the gift.
my blog post http://23.95.102.216/viewtopic.php?id=448210
22 octubre, 2021 a las 10:50
Great article! That is the type of info that should be
shared around the net. Disgrace on Google for now not positioning this put up upper!
Come on over and discuss with my site . Thank you =)
22 octubre, 2021 a las 11:19
Thank you for the good writeup. It in reality was once a amusement
account it. Glance advanced to more introduced agreeable
from you! By the way, how could we communicate?
22 octubre, 2021 a las 11:40
This is the perfect web site for everyone who
would like to understand this topic. You realize a whole lot its almost tough to argue with
you (not that I personally will need to…HaHa). You definitely put a fresh spin on a topic that has been written about for years.
Excellent stuff, just great!
25 noviembre, 2021 a las 19:26
Thanks for finally talking about > Introducción a los servicios
en Angular – Java desde 0 < Loved it!
13 diciembre, 2021 a las 13:13
Awesome blog! Is your theme custom made or did you
download it from somewhere? A design like yours with a few simple adjustements would really make my blog shine.
Please let me know where you got your design. Bless you
4 enero, 2022 a las 8:35
I blog quite often and I genuinely appreciate your information. Your article
has truly peaked my interest. I am going to take a note of your blog
and keep checking for new details about once a week. I subscribed to your Feed as well.
4 enero, 2022 a las 10:32
When I initially left a comment I seem to have clicked on the -Notify me when new comments are added- checkbox and from now on every time a comment is
added I recieve 4 emails with the exact same comment.
Perhaps there is an easy method you are able to remove me from that service?
Kudos!
31 enero, 2022 a las 19:51
I’ve beеn browsing online more than 3 hours today, yet I nevsr found any interesting article like yours.
It is pretty worth enouցh for me. In my view, if
aⅼl web owners and blօggers made good content as
you did, tthe internet wіll be a lot more useful than ever before.
My ԝebрaɡe debt consolidation
1 febrero, 2022 a las 1:05
Firset off I would like tօ say ѕuperb blog!
I had a quick question that I’d like tо ask if you do nnot mind.
I waѕ curious to know howw you center yourself aand clear
your thougһts before writing. I have had trouble clearing my mind
in gettig myү thougfhts out there. I truly do
enjoy writing but it jսst seems like the first 10 to 15 minute are generally wasteⅾ just trying tto figure out how to
begin. Any recommendations or hints? Cheers!
My web-site; debt consolidation (https://secure.hi5.com/consolidationresource)
1 febrero, 2022 a las 21:59
My family all the time say that I am wasting my time here at
web, except I know I am getting experience daily by reading such pleasant posts.
2 febrero, 2022 a las 0:02
Quality content iss the crucial tⲟo interest the peoρⅼe to go to
see the site, that’s what this web pazge iis provіding.
my web page; debt consolidation (http)
3 febrero, 2022 a las 18:06
I am in fact happy to read this blog posts which includes plenty of useful information, thanks for providing these
data.
7 febrero, 2022 a las 0:12
I really like what you guys are usually up too.
Such clever work and reporting! Keep up the terrific works guys I’ve included you guys to
blogroll.
16 febrero, 2022 a las 22:09
Wow that was strange. I just wrote an incredibly long comment but after I clicked submit my
comment didn’t appear. Grrrr… well I’m not writing all that over again. Regardless,
just wanted to say superb blog!
1 marzo, 2022 a las 15:57
Greetings from Los angeles! I’m bored to tears at work so I decided to
browse your blog on my iphone during lunch break.
I really like the information you provide here and can’t wait to take a look when I get home.
I’m shocked at how quick your blog loaded on my cell phone
.. I’m not even using WIFI, just 3G .. Anyhow, very good site!
16 marzo, 2022 a las 3:58
We will teach you how to earn $ 7000 per hour. Why?
We will profit from your profit.https://go.binaryoption.ae/FmUKhe
29 marzo, 2022 a las 2:07
Thanks to my father who told me on the topic of this web site,
this web site is truly awesome.
18 abril, 2022 a las 1:45
I’d like to find out more? I’d like to find out more details.
21 abril, 2022 a las 9:18
I was able to find good information from your content.
24 abril, 2022 a las 23:05
I think the admin of this web site is actually working hard in support
of his web page, since here every information is quality based material.
15 mayo, 2022 a las 14:37
Hello! This is my first visit to your blog! We are a team of volunteers and starting a new
project in a community in the same niche. Your blog provided us valuable information to work on. You have done a outstanding
job!
18 mayo, 2022 a las 12:15
Hey! Someone in my Myspace group shared this site with us so I came to take a
look. I’m definitely enjoying the information. I’m bookmarking and
will be tweeting this to my followers! Great blog and great design and style.
15 junio, 2022 a las 2:42
Howdy, i read your blog occasionally and i own a similar one and i was just curious if you get a lot of spam comments?
If so how do you protect against it, any plugin or anything you can recommend?
I get so much lately it’s driving me mad so any support is very
much appreciated.
17 junio, 2022 a las 6:34
We will teach you how to earn $8000 per hour.
Why? We will profit from your profit.http://binaryoptionsreview.eu/how-to-earn-9-000-binary-options-trading/
3 julio, 2022 a las 7:05
Thanks for any other informative blog. The place else could I get that kind of
information written in such an ideal method? I have a
project that I am simply now working on, and I’ve been on the look out for such info.