How To Make Angular Code More Reusable
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- čas přidán 9. 07. 2024
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From this video, you will learn why composition is much better than inheritance and Angular 15 makes directive composition much easier by introducing the new Dirctive Composition API. It helps you to split behavior among different directives and reuse them in components that need that behavior. I hope you will like the video and if so, please share it with your friends and colleagues. Enjoy!
Source code for this tutorial:
github.com/DMezhenskyi/angula...
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🕒 Time Codes:
00:00:00 - Intro;
00:00:44 - Inheritance vs Composition in Action;
00:06:03 - Angular Composition API in Action;
00:14:04 - Console Ninja Integration;
00:15:21 - Other tips about HostDirectives;
00:18:36 - Outro;
#angular - Věda a technologie
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you should change the channel's name, this channel deserves to be called "Angular master" or "Angular sensei"
Haha :) I will leave those names for real Masters and Sensei. I am just a regular Angular dev with relatively good experience and some video editing skills ;)
As always, very well explained Dmytro! Love this feature.
Great, as usual! Thanks!
That is an incredible feature, that will make my component library at work so much better!
I just wish that we can fill inputs of host-directives somehow in the component. You injected the disabled-directive into prevent-default-directive, which softly connects those directives. Sure it can be made optional, but we need to add every directive that wanna use the prevent-default-directive.
Another great video. Thanks for sharing!
Wow, this was incredibly informative! I can definitely use for my reusable components. Many thanks!
Thanks for providing very interesting insights and techniques about using directives.
Thanks, well explained.
Thank you a lot! Really cool feature. I wish I learned it months ago! I used to use inheritance.
Great stuff!!!
Fantastic video, my friend!!! I genuinely admire both your content and your teaching style. Thank you wholeheartedly for generously sharing your expertise with us humble learners.
Great video!
Thanks a lot ! This is a very informative video. The best Angluar channel for me.
Heads of to you man for deep content
great video!!!
Nice technique!
Very well explain as always!!!!
Thank you, Dany :) Glad to hear that from you.
Thank you very much for such a thorough explanation, it was very usefull!
I hope so 😊 thank you.
Brilliant!!
🙌
Clear and interesting. I will continue to follow you.
Thanks for your feedback:)
amazing, thank you for sharing
You are welcome 🤗 there will be more.
Thanks for another useful video, Dmytro ) I just started researching this topic today) p.s special thanks for adding source codes to tutorials, it helps a lot)
You are welcome, Gagik! Thank you for your feedback :)
Awesome, thank you
You're welcome! There will be more :)
yes learned something new
Awesome! That was the goal of the video and the whole channel ;)
I would be very interested in your take on how to structure a modern angular project(standalone only/ngrx..).Great videos all around.😊
thanks again !
You are welcome:)
It was great
Greate!
Amazing
Glad you like it 👍🏻
Thanks for another great video. I liked the intro for the insight into HostBinding. I've heard that directives aren't used enough by developers. I wonder if it's because it's quite a low level thing that you would use if you were building your own UI library, whereas a lot of Angular devs (I presume) are working with external UI libraries like material, ng-bootstrap, primeng etc)
Glad you liked it :) Yeah, I also have a feeling that the angular directives are quite underestimated and are used not as often as they could be. One of my theories is that many people come to Angular from other frameworks like React where there is no such concept of Directives and they tend to move the already familiar way based on components. Also, maybe there are luck of educational materials that highlight the strengths of angular directives... but this is something that I could fix ;)
Hey Dmytro! Nice video, this API is quite nice for simple use cases indeed. But what I do not like is that you have to manually type out all the inputs and outputs of each directive, it would've been really great to have an option to just enable all inputs/outputs on the host directive without typing each of them separately.
Also I wonder if this feature only available at a build time phase or is there a way to dynamically add host directives to already existing directives that you do not have control over, for example can you add host directives to existing 3rd party directive from another library?
And finally, there is just one more way to avoid code duplication without using this angular feature - use mixin pattern, you can easily make each directive as a mixin and then apply them on specific components exactly where needed, so you would still technically use inheritance but it will not be static and you will be able to compose multiple mixins where and how you want to =)
But mixins are purely static and applied at class definition so you definitely will not be able to augment existing directives/components with them but with angular host directives it seems like it should be possible to achieve dynamic augmentation at least in theory but I'm not sure if angular team implemented/exposed such feature, so would be cool to hear what you know about it!
Thanks for your videos, I'm not working with Angular for a long time but you are keeping me up-to-date with all latest angular stuff =)
Stay safe, cheers!
Hey Alex! Thank you for your as-always detailed feedback and thoughts, I always much much appreciated it :)
By "enabling all inputs/outputs" do you mean by default or your idea is to have something like hostDirectives: ['*']? I think it would be an interesting idea and worth a dedicated GitHub issue because indeed it might be sometimes useful.
Regarding the 3rd party directives and dynamic directive augmenting. As far as I know, currently, it is possible only at build time :(
Yep, mixins are also an option and it is used by Angular Material, however, with mixins you can inherit only class properties/methods but Angular features like @Input(), etc will not be working there and mixins are problematic for template type checking. Also, mixins syntax looks a little bit clumsy and boilerplate-ish but it is a matter of taste :D
Regarding the dynamic directive augmenting at runtime, tbh I don't have any information about it but my quick research led me to this comment github.com/angular/angular/issues/11716#issuecomment-373193097 which made me think that it won't be probably implemented but who knows, maybe something will change. Angular evolves so much and fast last time.
Glad to hear that my videos help you :) Get back to Angular family soon :D
Good luck anyway!
Aaagh, I was about to go crazy with directive composition, but fortunately watched video till the end :D
:) Don’t afraid to use Composition API, just keep in mind that moment with extra memory allocation and avoid it when it makes sense. In most cases you should not experience any problems with Composition API 😉
Me too 😄
Cool stuff
Agree! Thanks for feedback, Paulo.
Great video as usual. Thank you.
I have a question about the part when you used inject function to inject CanDisable directive, where it will get the correct instance?
Also what if the host component didn't have the CanDisable directive?
Thanks for this clear explanation about Directive Composition API. Very interesting topic.
Also interesting to know that a directive can also uses hostdirectives. I didn't like the example of it because it has bidirectional dependency between the two directives.
Wonder if there is a better usecase for it.
An alternative approach (without using DI) that first came to my mind is introducing the @Input() disabled; also for the CanPreventDefault directive and exposing it from CanDisable one too. Then the 'disabled' input should be always in sync for both directives in this case and it removes coupling via DI. (here is the code example - github.com/DMezhenskyi/angular-directive-composition-api-demo/blob/alternative-without-di/src/app/directives/can-disable.directive.ts#L9).
If by bidirectional dependency you mean "circular dependency" I wouldn't say that it is the one. The circular dependency you would get if CanDisable injects CanPreventDefault and at the same time CanPreventDefault injects CanDisable. The hostDirective doesn't inject declared directives but just instructs that the directives should be applied to the host when the component is initialized and it is pretty much the same as if declaring them explicitly in the template.
This pattern (when one directive injects another one) you can see quite often in Angular source code too. For example, the NgModel directive injects the same way ControlValueAccessor directives in Angular Forms :)
If i am using a directive wrapper for another directives "hostDirective" how can i achieve the exportAs from the nested directives in the top level directive?
Ta for the video. Can u explain how can u define a hostdirective and inject the directive onto its declared host direcrive. Isnt it circular depwndemcy?
Thanks for the video!
Similar to another one I've seen before, but would like to know if this pattern makes sense when you have "base" logic to share between components that have small different details (Also thinking that initial data set on OnInit). Or using BaseComponents is still the best practice?
Great video! Was wondering if you could do a video on how to import an external Javascript File into Angular 16. I know it sounds simple, but I haven’t seen any tutorial that actually works in the new Angular version
i would like to see a video about decorators in angular
So for the large datatable, if we cannot go this way performance-wise for a button with its reusability, what do you suggest then?
If you put those buttons in a table, how about the performance? Btw is there any chance you do it using decorator class?
Your way of teaching and explaining the concept was a real game changer🎉🎉🎉. Please keep it up.
I noticed that injecting canDisable directive into CanPreventDirective can cause circular dependency. Please validate
Hi! Thank you for your kind words. Regarding your question: You will get circular dependency if the CanDisable directive injects CanPreventDefault one and at the same time CanPreventDefault injects CanDisable. The hostDirective doesn't inject the declared directives but just instructs that the directives should be applied to the host when the component is initialized and it is pretty much the same as if declaring them explicitly in the template.
Hey Dmytro, Nice Video. I have question regarding dynamic CSS file loading. In my project, I am using multiple lazy loaded module. I want to load specific module related global css file. That global css file will only apply to its child components.
Very informative video.
I just have a question, as you said after adding hostDirectives array in the component.
Does it add the directive to all the elements available in the html?
Hi! Thanks for your feedback.
No, directives will be applied only to the component host element
Hi, Could you create a video on Angular Universal? It is so confusing to understand how things are happening in the background.
reason to mark base class with @directive() ?
Technically component is directive with a template. You wouldn't have lifecycle hooks if you didn't mark the base class as a directive.
Yep, as @MichalSmolinsky said, you have to decorate base class with @Directive annotation to inherit Angular features like @Input(), @HostBinding(), etc. it is required since Angular 9 when Ivy renderer became default.
So it is a good practice to remove the selector directive to avoid it being displayed elsewhere than in hostdirective ? Thanks for this amazing video !
I think it needs some time to understand it because this feature is relatively new. I see it useful if the directive is intentionally designed in a way that can work only with specific directives in tandem as a hostDirective, so removing the selector can guarantee that this directive won't be applied by mistake anywhere else in the application... but also, can't come up so far with an explicit real-life example of it... And this is the reason why I asked to discuss this because I hope to learn something from the community :)
I don't understand how you can inject(CanDisableDirective) into the CanPreventDefaultDirective, how does it work? Do you have some video explaining it? How the injector knows which directive to inject?
Hi 🙂Try to check my video about Dependency Injection - czcams.com/video/G8zXugcYd7o/video.htmlsi=TMcQ_4XF8BlU6dqG
Do we realy need use separate component for the button tag? Its just simple element and you can mix styles of button applies different global class for this purpose, without any wrapper of angular component.
In general, it depends on the features that the button should have. If the button has its own HTML structure, makes a content projection, etc that it makes sense to have it as a component. If it has only some custom props like 'color' then it could be just a directive. If it is only about styling - your approach can also be a working option. In the video, the button was made as a component just for demo purposes, so please don't take it as an example of the proper component architecture design or production-ready code :) For tutorials, the implementation of some indirectly related building blocks is very often intentionally simplified or artificially adjusted to some concrete demo use cases.
I have a question. Let's say that I have 8 common inputs in 2 different components. I can't handle them with binding a class or something since they are all object types. How can i handle this case? Should i stick with directives or abstract component?
Just as a side note: directives used in hostDirectives need to standalone. Also, in this scenario you could also solve this without hostDirectives by simply using the directive selectors to target only the components you need to apply them to. Seeing Material directives can’t be used yet with this APi, that might be a good alternative.
I have a question regarding passing multiple input props to an Angular component. In your previous videos, you demonstrated how to pass individual props like this:
I'm curious to know if there is a way to pass all the props using a single object, like this: . Is it possible to achieve this in Angular?
It looks like you are coming from React world and looking for {...props} option :) Unfortunately, it is not possible in Angular yet.
Is it possible to add a hostDirective conditionally? For instance, based on a value that we recieve in constructor of a host component.
Maybe by wrapping a directive in another directive that has boolean input parameter 🙂
Hi Andriy! Thanks for your question. Unfortunately, it is not possible as far as I know :)
@@DecodedFrontend Appriciate an instance response, Дмитро 🇺🇦 :D
At least I found another useful feature:
We can provide input params from inside the host element, since we can set propreties of an injected directive, not only get them as you showed at 14:00
private canDisableDir = inject(canDisableDirective);
this.canDisableDir.disabled = isDisabled;
It seems that applying styles with directives is still not supported properly? :( That's a bummer, because it makes a lot of functionality composition scenarios awkward, since plenty of functionality has corresponding complex styling.
Love the thumbnail 😆👍
Thank you! I was trying hard to make it happen :D
@@DecodedFrontend Hardwork paid off, you nailed the pose 😎
And the video is amazing as always, can't wait to play around with Directives. Thanks and keep up the quality content 👍
I have a doubt about, how can i implement @ContentChild in a hostDirective ? I tried to but all i get is undefined
Well nice, but all directives have to be on the same level of the component ... if they are spread in the HTML inside the component, how will Angular knows which directive is applied on which element ?
but that's actually the point and that's why they are called hostDirective because are being added to the component host element :) The directives that have to be used in the component view, you have to apply manually to a DOM elements as before.
@@DecodedFrontend :)
It looks strange to me that you have to inject a directive that composes host-directive inside host-directive to reach its fields. What should I do if I want to use that host-directive with different directives?
There is only one way I can see to add to directive provider `providers: [{ provide: Preventable, useExisting: CanDisableDirective }]` where Preventable is the base class for directives that compose host-directive. Then reach these directives inside the host-directive by `preventable = inject(Preventable);`.
You can use the "optional" resolution modifier to prevent failing if some directive wasn't found and adjust your logic accordingly but it depends on the concrete use case. The goal was just to show that it is possible to access directives via DI rather than to show a production-ready code snipped. Also, if you don't mind I will copy-paste my answer for a similar question here above :)
"An alternative approach (without using DI) that first came to my mind is introducing the @Input() disabled; also for the CanPreventDefault directive and exposing it from CanDisable one too. Then the 'disabled' input should be always in sync for both directives in this case and it removes coupling via DI. (here is the code example - github.com/DMezhenskyi/angular-directive-composition-api-demo/blob/alternative-without-di/src/app/directives/can-disable.directive.ts#L9).
If by bidirectional dependency you mean "circular dependency" I wouldn't say that it is the one. The circular dependency you would get if CanDisable injects CanPreventDefault and at the same time CanPreventDefault injects CanDisable. The hostDirective doesn't inject declared directives but just instructs that the directives should be applied to the host when the component is initialized and it is pretty much the same as if declaring them explicitly in the template.
This pattern (when one directive injects another one) can see quite often in Angular source code too. For example, the NgModel directive injects the same way ControlValueAccessor directives in Angular Forms :)"
Amazing video! 🚀
How could you make the Console Ninja extension work with Angular? 🤔
Hey :) Thanks for your comment. As far as I remember I didn’t do anything extra with Console Ninja. I just installed it and just worked.
W thumbnail
Topic Suggestion: Component composition through mixins (such as those used in Angular Material)
Mixins are bad practice, since they can lead to an excessive amount of logic.
so, hostDirective needs to be repetitive each time you need to use it in the template.. hmm
Am not sure I understand you correct :) Actually, other way around, the hostDirective allows you to avoid code duplication in the template
run the build of your angular application and see the code generated inside the dist directory. maybe you uninstall the ninja extension
Thanks for your comment. I just did it but I don't see anything unexpected. Am I missing something?
@@DecodedFrontend after a few days I installed the extension I realized that it was injecting totally obfuscated javascript code in the middle of my build files for production
It's been about 2 months since this happened to me.
@@GuiSeek Maybe they fixed that because I didn't experience anything like that... and tbh I can hardly imagine how the extension code could be leaked into the application bundle 🤔
@@DecodedFrontend Unfortunately it still is, I just reinstalled and found the injected and obfuscated code here again... run the build configured for production and search for "_console_ninja"