#08 View Template of Component | Angular Components & Directives| A Complete Angular Course
Summary
TLDRThe lecture explains how to create and use a component in Angular, focusing on rendering its view template. It discusses two methods: the 'template' property, which embeds HTML as a string in the TypeScript file, and the 'templateUrl' property, which references an external HTML file. While the 'template' method can handle small amounts of HTML, it becomes cumbersome and error-prone with larger code. The 'templateUrl' method is preferred for separating HTML from TypeScript, making the code more maintainable. The lecture concludes by demonstrating how to implement these techniques.
Takeaways
- 📦 Angular components can be used by referring to their selectors, which are treated like HTML elements.
- 📄 The HTML rendered by a component is known as its view template.
- 📛 The template property in the component is used to define the HTML when there are only a few lines of code.
- 💻 Using template URL allows developers to specify the path to an external HTML file, making the code more manageable.
- 🗂️ It's recommended to use template URL when there are many lines of HTML to avoid cluttering the TypeScript file.
- 🔧 The template property can lead to maintainability issues since it mixes TypeScript and HTML code in one file.
- 🚫 Errors in HTML within the template property are harder to detect since they only appear at runtime, not during compilation.
- 📐 A large amount of HTML code in the template property can make the code messy and difficult to manage.
- 📏 Separating HTML into a template URL promotes better code organization and maintainability, even for small HTML snippets.
- 🖌️ The next step after defining the view template is to style it, which will be covered in the following lecture.
Q & A
What is the view template of a component in Angular?
-The view template of a component is the HTML that tells Angular how to render the component. It defines the structure of the component's HTML content.
How do you use a component's selector in Angular?
-To use a component's selector, you add the selector like an HTML element in another component's HTML file. Angular then replaces that selector with the component's view template.
What is the role of the 'template' property in a component?
-The 'template' property allows you to specify the view template of a component directly as an inline HTML string within the component’s TypeScript file.
Why is the 'template' property not suitable for large HTML content?
-Using the 'template' property for large HTML content can make the code messy and harder to maintain because the HTML is written as a string within the TypeScript file.
What is the 'templateUrl' property, and when should you use it?
-The 'templateUrl' property specifies the path to an external HTML file that contains the view template for the component. It should be used when the HTML content is large or when you want to separate the HTML from the TypeScript code for better maintainability.
What are the disadvantages of using the 'template' property?
-Disadvantages of using the 'template' property include mixing HTML with TypeScript, lack of compile-time error detection for HTML mistakes, and the potential for messy code if the HTML is large.
Why is it beneficial to use 'templateUrl' even for small HTML templates?
-Using 'templateUrl' is beneficial even for small templates because it keeps the HTML code separate from the TypeScript code, making it easier to maintain and less prone to errors.
What happens when Angular compiles the component with a selector and a view template?
-When Angular compiles the component, it replaces the selector with the HTML content specified in the view template, either defined via the 'template' or 'templateUrl' property.
What issue arises with using 'template' when an HTML tag is not closed properly?
-If an HTML tag is not closed properly while using the 'template' property, the error won't be detected at compile-time. Instead, it will only be noticed at runtime, making debugging harder.
What should be done if the HTML view template is styled improperly?
-If the view template is styled improperly, CSS or other styling methods can be applied to the component, which will be covered in a subsequent lecture.
Outlines
🔧 Introduction to View Templates in Angular Components
In this paragraph, the concept of a view template in Angular components is introduced. A view template defines the HTML rendered when a component's selector is used. The header component is used as an example, where the 'app-header' selector renders an H3 HTML element. This basic template is directly written in the component using the 'template' property.
📝 Using the Template Property for Simple HTML
This section elaborates on the 'template' property for simple HTML, noting that it works well for short snippets like a single HTML tag. However, if more HTML elements are added, such as paragraphs, the code quickly becomes messy. The 'template' property is practical for small templates, but for more extensive HTML, it becomes inefficient.
📂 Introducing Template URL for Complex Templates
The paragraph discusses the alternative to the 'template' property, the 'templateUrl' property. Instead of directly embedding HTML within the component, developers can specify an external HTML file's path. The process of creating and linking the external file (header.component.html) in Angular is explained, making it easier to manage larger templates.
💻 Rendering HTML Using Template URL
Here, the HTML from the external file (header.component.html) is rendered wherever the 'app-header' selector is used. A demonstration is given on how this external HTML is shown in the browser. Although the rendered HTML is unstyled, the use of 'templateUrl' allows for better code organization, especially for larger templates.
🚨 Downsides of Using Template Property
This paragraph highlights the disadvantages of using the 'template' property. Mixing TypeScript and HTML in the same file makes the code less maintainable, and errors in the HTML might not be caught during compilation, only during runtime. Furthermore, large amounts of HTML code can make the TypeScript file cluttered and difficult to maintain.
✅ Preference for Template URL for Better Maintainability
The final paragraph emphasizes the advantages of using 'templateUrl', even for small HTML templates. By keeping HTML and TypeScript separate, the code becomes more maintainable. It reiterates that while 'template' can be used, 'templateUrl' is generally the better choice for maintaining a cleaner, more organized codebase.
Mindmap
Keywords
💡Component
💡Selector
💡View Template
💡Template Property
💡TemplateURL
💡Typescript
💡Maintainability
💡Runtime Error
💡Compilation Time
💡HTML File
Highlights
Introduction to creating and using components in Angular, utilizing the component's selector like an HTML element.
View template of a component is the HTML that Angular uses to render a component.
Components are created with a selector, which is used in the HTML file to render the component.
Angular renders HTML based on the template property when the component selector is used.
The template property is useful when there's a small amount of HTML, like a few lines.
When there are multiple lines of HTML, using the template property can make the code messy and difficult to maintain.
For larger HTML content, Angular provides the templateUrl property to reference an external HTML file.
The templateUrl property allows developers to keep HTML and TypeScript separate, improving maintainability.
The HTML file specified by templateUrl contains the HTML that gets rendered when the component selector is used.
When using templateUrl, the HTML is written in a separate file, making it easier to manage complex templates.
Mixing HTML and TypeScript in a single file using the template property can make code harder to maintain.
Errors in HTML defined with the template property are only detected at runtime, not during compilation.
Using templateUrl avoids errors related to HTML syntax by separating concerns between HTML and TypeScript.
The template property results in messier code with large amounts of HTML, making it less readable and maintainable.
Using templateUrl is preferred by the speaker even for small HTML content, as it promotes better code organization and maintainability.
Transcripts
in the last lecture we learned how to
create and use a component now when we
create a component in order to use it we
use its selector like an HTML element
and whenever we use the selector of a
component like an HTML element there
some HTML gets rendered
and that HTML is called as the view
template of that component
so basically the view template of a
component is a form of HTML that tells
angular how to render a component
in the last lecture when we created this
header component there we are specifying
a selector called app header
and then we are using this selector in
our app component.html file and we are
using it like an HTML element
so when we are using it like this in
place of this when the angular
application will run in place of this it
has to render some HTML
and we are specifying that HTML using
this template property
so in place of this app header this S3
element will be rendered so if I go to
the web page
there you can see that S3 element has
been rendered
so basically we are specifying The View
template of this header component using
this template property
now we can use this template property
when we have very few lines of HTML for
example here we have only one line of
HTML we have only S3 element here
but if we want to have a lot of HTML
code then specifying it here is a bit
cumbersome for example let's say I also
want to have a paragraph element
and in that paragraph element let me go
ahead and let me write some text then if
I also want to have another paragraph
then again I will add it here inside
this single quotes So in this way this
HTML will become a little bit messy
right we can use this template property
whenever we have very few lines of HTML
for example let's say we have only two
or three lines of HTML in that case
using this template property is okay
because in that case two or three lines
of HTML will not make it messy
but if we have more lines of HTML then
instead of using this template we can
use another property called as template
URL so using this template URL also we
can create a view template for the
component
but when we use this template URL there
we don't assign any HTML
there we need to specify the path of an
HTML file
and the path of this HTML file can be
any HTML file so here we need to now
specify the path of the HTML file which
we want to render whenever this selector
is used in our angular application for
that inside this header folder let's go
ahead and let's create a new file again
the file name should be the component
name in this case the component name is
header Dot component and then the file
extension here we are going to create an
HTML file so the file extension will be
HTML
okay and now in our header component.ts
for this template URL let's specify the
path of this header component.html so it
is in the current directory
and in there we have
header Dot
component dot HTML file
okay
so here we are specifying the path of
the HTML file which should be rendered
wherever we are using this app header
selector
now in this header component.html we can
write some HTML in order to save some
time I have already created some HTML
so let me copy this HTML from here let's
go back to vs code and there let's paste
it
so now wherever we will use this app
header like an HTML element there the
content of this header component.html
will be rendered so if I save the
changes now and if we go to the web page
there you see some HTML has been
rendered here now this HTML is not
styled that's why it looks like this but
we are going to style it in our next
lecture but as you can see
in place of
this app header now the HTML content of
header component.html is being rendered
okay so there are two ways to specify a
view template for your component class
either by using template URL property
like we are doing here
in that case to this template URL
property we need to assign the path of
the HTML file which we want to use as
the view template
or we can also use template property in
that case to that template property we
assign the HTML as string
now when we use template property for
creating the view template there are
some disadvantages there
first of all if we use template property
for creating the view template of our
component in that case we are mixing the
HTML and typescript code which makes the
code less maintainable because in the
same typescript file we have a
typescript class and they only we are
also writing some HTML code so basically
we are mixing the HTML and typescript
code and it makes the code less
maintainable
then since HTML is written as a string
so to the template property we assign a
string and inside that string we write
the HTML code right so if there is some
error there let's say we have missed
some closing tag for an element or
something like that we will not come to
know about it during the compilation
time we will only come to know about it
during runtime so that is another big
disadvantage here
and also if the number of lines of HTML
code is huge it will make the code messy
and non-maintainable
that's why I always prefer to use
template URL property for creating the
view template for my components even
though the HTML code is going to be
maybe one or two lines of code but still
I prefer template URL because in that
way I am separating my HTML code from my
typescript code
all right so in this lecture we learned
what is a view template and how to
create a view template for a component
we learned about two ways we can either
use template property of the add
component decorator or we can use
template URL property for creating a
view template
this is all from this lecture if you
have any questions then feel free to ask
it
in the next lecture let's learn how we
can style The View template of our
component
foreign
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