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$http service in AngularJS Video Lecture | Learn and Understand AngularJS : For Beginners - Front-End Programming
FAQs on $http service in AngularJS Video Lecture - Learn and Understand AngularJS : For Beginners - Front-End Programming
| 1. What is the purpose of the $http service in AngularJS? |  |
Ans. The $http service in AngularJS is used to make HTTP requests to a server and retrieve data asynchronously. It provides a simple way to interact with RESTful APIs and retrieve data from a server.
| 2. How do you make an HTTP GET request using the $http service in AngularJS? | |
Ans. To make an HTTP GET request using the $http service in AngularJS, you can use the following syntax:
```
$http.get(url)
.then(function(response) {
// handle success response
}, function(error) {
// handle error response
});
```
You need to provide the URL of the server you want to retrieve data from. The response from the server can be handled in the success callback function.
| 3. Can the $http service in AngularJS handle HTTP POST requests? | |
Ans. Yes, the $http service in AngularJS can handle HTTP POST requests. To make a POST request, you can use the following syntax:
```
$http.post(url, data)
.then(function(response) {
// handle success response
}, function(error) {
// handle error response
});
```
You need to provide the URL of the server you want to send data to, and the data you want to send in the request body. The response from the server can be handled in the success callback function.
| 4. How can you set headers in an HTTP request using the $http service in AngularJS? | |
Ans. You can set headers in an HTTP request using the $http service in AngularJS by providing a configuration object as the second parameter to the $http method. Here is an example:
```
$http.get(url, {
headers: {
'Content-Type': 'application/json',
'Authorization': 'Bearer token'
}
})
.then(function(response) {
// handle success response
}, function(error) {
// handle error response
});
```
In this example, we set the 'Content-Type' and 'Authorization' headers in the GET request.
| 5. How can you cancel an HTTP request made using the $http service in AngularJS? | |
Ans. To cancel an HTTP request made using the $http service in AngularJS, you can use the `timeout` property in the request configuration object. Here is an example:
```
var canceler = $q.defer();
$http.get(url, {
timeout: canceler.promise
})
.then(function(response) {
// handle success response
}, function(error) {
// handle error response
});
// To cancel the request
canceler.resolve();
```
In this example, we create a canceler using `$q.defer()` and set it as the value of the `timeout` property. If we want to cancel the request, we can call `canceler.resolve()`.
Text Transcript from Video
this is part 18 of handler J's tutorial
in this video we'll discuss HTTP service
in angular in angular
there are several built-in services
dollar HTTP service is one of them in
this video we'll discuss another
built-in service dollar log it's also
possible to create our own custom
services in angular at this point
several questions come to our mind what
are services in angular when should we
be creating services in angular how to
create our own custom angular services
where do these services fit in an
angular application architecture what
are the benefits of using services I
will answer all these questions in a
later video the reason for postponing
this discussion is that it is easier to
understand the concept of angular
services and the benefits they provide
once we understand how to use one or two
built in angular services so let's start
our discussion with the HTTP service the
HTTP service is used to make HTTP
requests to a remote server
in fact we looked at an example of how
to do that in our previous video session
HTTP service is a function that has a
single input parameter that is a
configuration object in this example
right here we are issuing a get request
to this URL employee service dot s mx4
slash get all employees now if you look
at this configuration object right here
they're only using two properties of it
but this object has got several
properties and for the complete list of
properties please visit this URL right
here so on this page you can see the
list of all properties supported by the
configuration object at the moment we
are only using these two properties
method and URL as we move along in this
course we'll discuss how to use these
other properties now if you recollect
the example that we worked with in the
previous video session notice here we're
using the get shortcut method of the
HTTP service instead of using this get
shortcut method we can use this HTTP
service as a function when we do that we
have to pass it the configuration object
so I'm going to open the parentheses
here
and close it right here so we have an
object there and when we use the object
we have to specify at least two
properties the method that we want to
use to issue that request so we want to
issue a cat request and this is the URL
to which we want to issue that get
request let's save our changes and when
we reload this page it should continue
to work exactly the same way as before
shortcut methods like get post put
delete etc but also available to be used
with the HTTP service we discussed an
example of how to do that using the
shortcut method get in our previous
video the HTTP service returns a promise
object this means the functions are
executed asynchronously and the data
that these functions return may not be
available immediately because of this
reason you cannot use the return value
of the HTTP servers as shown right here
notice here we are assigning the return
value of the HTTP service to this
employee's property on the scope we
cannot do this right away like that
that's because the HTTP returns a
promise object so instead we use the den
method so in this example notice that we
have chained the den method with the
sket method and to this den method we
are passing an anonymous function as a
parameter so this is called the success
callback function this is the function
that is called when the request
completes successfully so when the
request is completed successfully we get
a response from the server that's passed
to this success callback function and
this response object has got several
properties and among those several
properties data is one of them which we
use to retrieve the data so we are
retrieving the data and then assigning
that to the employee's property on the
dollar scope object which is then
available in the view now to inspect all
the properties of this response object
we can use another built in angular
servers which is log this log service
has got info method which we can use and
once we pass to that info method that
and so object it's going to log that
object to the console and then we can
use the developer tools of the browser
vendor and then see what are the
different properties and what
information they contain let's actually
look at an example of doing that right
now
so just like how we have injected the
HTTP service to this function I'm going
to inject the log service and then
within this success callback function we
can use that log service provided by
angular it has got the info function
under this function I'm going to pass
the response object let's save our
changes and when we reload this page and
when we launch the developer tools the
response object should have been logged
to the console vendor so we are on the
console vendor at the moment load is
that we have got an object here and this
object has got several properties the
first property here is the config object
the config object you know that we have
used along with the HTTP servers
remember we have specified two
properties method the method was care
that we used and this is the URL to
which we want to issue the get request
so the config object contains the
information about the request object and
we also have the data property the data
property contains the data that the web
service has written we got an array of
employee objects so we have got an array
here with five objects within it and
each object should have the properties
that we see here ID name gender celery
and it also has got the headers
information status and status text so
another very useful service to log the
objects to the console very useful
especially when you're debugging angular
applications if there is an error
processing the request the error
callback function is called if you look
at you know the den function here at the
moment we are only passing one anonymous
function as a parameter which is the
success callback function in addition to
the success callback function we can
also pass another parameter that is
another anonymous function which is the
error callback function that is the
function that will be called when there
is an error processing request
so let's actually pass another anonymous
function
and what we are going to get back is a
reason object so this is the anonymous
function that is called if there is an
error processing the request and let's
say we want to display that error
message to the user so to this koop
object I am going to attach another
property dot error and again this reason
object has got several properties and if
you want to see all the properties again
you can log it to the console just like
how we have logged the response object
so this reason object again has got the
data property which contains the
information about the error so we are
storing that within the error property
of the scope object which is available
within the view so what I'm going to do
is just about this table within the view
I'm going to use that error property and
display the error message let's include
to HTML break elements so there's some
space between the table and the error
message all right now let's also log the
error object to the console so I'm going
to use the log service and use the info
method and then pass the reason object
all right so let's save all these
changes and let's make this web service
fail deliberately so I'm going to remove
s from the name of the method okay so
let's reload this and see what what
we're going to get look at that for some
reason we see the data-binding
expression instead of the actual error
message let's see why is that that means
there's something wrong look at that
that's because we have a compilation
error here so let's fix that and let's
reload that and look at that we see the
error message invalid Operation
exception get all employee web service
method is not valid okay and that's
right and look at that you know we have
the internal service and there is an
object logged and again this object has
got several properties you know just
like the response object that we got
config data header status and status
text
now you can also create separate
functions and associate them as success
callback and error callback functions
now if you look at what we are doing
here we are passing these anonymous
functions you know as parameter values
to this then function instead of that
what we can do is create this function
separately so we can do something like
this so we are creating first a success
callback function and then an error
callback function and then we are using
those functions as values for the then
method let's actually look at that in
action so what I can do is with another
controller let's create a variable let's
call this success callback equals that's
going to be a function actually let's
cut that from there and paste it right
here and let's remove this login from
there similarly I'm going to create
another error callback function and what
we want to do actually
double-scoop dot data employees is the
property equals response dot data and
error callback what we want to do dollar
scoop dot error equals again response
dot data all right
so now we have two functions here so I
can use these functions as the values
for the den method so success callback
and error callback all right so let's
save the changes and let's fix that
error that we have so let's put that
right get all employees now it should
work without any error look at that we
get the employee's data now out of the
box the angular HTTP provides to default
transformations if the data property of
the request configuration object
contains a JavaScript object in fact
here it's a JavaScript object that we
are passing to our web server okay so if
it contains a JavaScript object it's
automatically converted into a JSON
object we got that transformation out of
the box without having to write any line
of code
similarly if JSON response is detected
from the web server it's automatically
converted into a JavaScript object so
out of the box you know these two
default transformations are provided by
angular thank you for listening and have
a great day
in this video we'll discuss HTTP service
in angular in angular
there are several built-in services
dollar HTTP service is one of them in
this video we'll discuss another
built-in service dollar log it's also
possible to create our own custom
services in angular at this point
several questions come to our mind what
are services in angular when should we
be creating services in angular how to
create our own custom angular services
where do these services fit in an
angular application architecture what
are the benefits of using services I
will answer all these questions in a
later video the reason for postponing
this discussion is that it is easier to
understand the concept of angular
services and the benefits they provide
once we understand how to use one or two
built in angular services so let's start
our discussion with the HTTP service the
HTTP service is used to make HTTP
requests to a remote server
in fact we looked at an example of how
to do that in our previous video session
HTTP service is a function that has a
single input parameter that is a
configuration object in this example
right here we are issuing a get request
to this URL employee service dot s mx4
slash get all employees now if you look
at this configuration object right here
they're only using two properties of it
but this object has got several
properties and for the complete list of
properties please visit this URL right
here so on this page you can see the
list of all properties supported by the
configuration object at the moment we
are only using these two properties
method and URL as we move along in this
course we'll discuss how to use these
other properties now if you recollect
the example that we worked with in the
previous video session notice here we're
using the get shortcut method of the
HTTP service instead of using this get
shortcut method we can use this HTTP
service as a function when we do that we
have to pass it the configuration object
so I'm going to open the parentheses
here
and close it right here so we have an
object there and when we use the object
we have to specify at least two
properties the method that we want to
use to issue that request so we want to
issue a cat request and this is the URL
to which we want to issue that get
request let's save our changes and when
we reload this page it should continue
to work exactly the same way as before
shortcut methods like get post put
delete etc but also available to be used
with the HTTP service we discussed an
example of how to do that using the
shortcut method get in our previous
video the HTTP service returns a promise
object this means the functions are
executed asynchronously and the data
that these functions return may not be
available immediately because of this
reason you cannot use the return value
of the HTTP servers as shown right here
notice here we are assigning the return
value of the HTTP service to this
employee's property on the scope we
cannot do this right away like that
that's because the HTTP returns a
promise object so instead we use the den
method so in this example notice that we
have chained the den method with the
sket method and to this den method we
are passing an anonymous function as a
parameter so this is called the success
callback function this is the function
that is called when the request
completes successfully so when the
request is completed successfully we get
a response from the server that's passed
to this success callback function and
this response object has got several
properties and among those several
properties data is one of them which we
use to retrieve the data so we are
retrieving the data and then assigning
that to the employee's property on the
dollar scope object which is then
available in the view now to inspect all
the properties of this response object
we can use another built in angular
servers which is log this log service
has got info method which we can use and
once we pass to that info method that
and so object it's going to log that
object to the console and then we can
use the developer tools of the browser
vendor and then see what are the
different properties and what
information they contain let's actually
look at an example of doing that right
now
so just like how we have injected the
HTTP service to this function I'm going
to inject the log service and then
within this success callback function we
can use that log service provided by
angular it has got the info function
under this function I'm going to pass
the response object let's save our
changes and when we reload this page and
when we launch the developer tools the
response object should have been logged
to the console vendor so we are on the
console vendor at the moment load is
that we have got an object here and this
object has got several properties the
first property here is the config object
the config object you know that we have
used along with the HTTP servers
remember we have specified two
properties method the method was care
that we used and this is the URL to
which we want to issue the get request
so the config object contains the
information about the request object and
we also have the data property the data
property contains the data that the web
service has written we got an array of
employee objects so we have got an array
here with five objects within it and
each object should have the properties
that we see here ID name gender celery
and it also has got the headers
information status and status text so
another very useful service to log the
objects to the console very useful
especially when you're debugging angular
applications if there is an error
processing the request the error
callback function is called if you look
at you know the den function here at the
moment we are only passing one anonymous
function as a parameter which is the
success callback function in addition to
the success callback function we can
also pass another parameter that is
another anonymous function which is the
error callback function that is the
function that will be called when there
is an error processing request
so let's actually pass another anonymous
function
and what we are going to get back is a
reason object so this is the anonymous
function that is called if there is an
error processing the request and let's
say we want to display that error
message to the user so to this koop
object I am going to attach another
property dot error and again this reason
object has got several properties and if
you want to see all the properties again
you can log it to the console just like
how we have logged the response object
so this reason object again has got the
data property which contains the
information about the error so we are
storing that within the error property
of the scope object which is available
within the view so what I'm going to do
is just about this table within the view
I'm going to use that error property and
display the error message let's include
to HTML break elements so there's some
space between the table and the error
message all right now let's also log the
error object to the console so I'm going
to use the log service and use the info
method and then pass the reason object
all right so let's save all these
changes and let's make this web service
fail deliberately so I'm going to remove
s from the name of the method okay so
let's reload this and see what what
we're going to get look at that for some
reason we see the data-binding
expression instead of the actual error
message let's see why is that that means
there's something wrong look at that
that's because we have a compilation
error here so let's fix that and let's
reload that and look at that we see the
error message invalid Operation
exception get all employee web service
method is not valid okay and that's
right and look at that you know we have
the internal service and there is an
object logged and again this object has
got several properties you know just
like the response object that we got
config data header status and status
text
now you can also create separate
functions and associate them as success
callback and error callback functions
now if you look at what we are doing
here we are passing these anonymous
functions you know as parameter values
to this then function instead of that
what we can do is create this function
separately so we can do something like
this so we are creating first a success
callback function and then an error
callback function and then we are using
those functions as values for the then
method let's actually look at that in
action so what I can do is with another
controller let's create a variable let's
call this success callback equals that's
going to be a function actually let's
cut that from there and paste it right
here and let's remove this login from
there similarly I'm going to create
another error callback function and what
we want to do actually
double-scoop dot data employees is the
property equals response dot data and
error callback what we want to do dollar
scoop dot error equals again response
dot data all right
so now we have two functions here so I
can use these functions as the values
for the den method so success callback
and error callback all right so let's
save the changes and let's fix that
error that we have so let's put that
right get all employees now it should
work without any error look at that we
get the employee's data now out of the
box the angular HTTP provides to default
transformations if the data property of
the request configuration object
contains a JavaScript object in fact
here it's a JavaScript object that we
are passing to our web server okay so if
it contains a JavaScript object it's
automatically converted into a JSON
object we got that transformation out of
the box without having to write any line
of code
similarly if JSON response is detected
from the web server it's automatically
converted into a JavaScript object so
out of the box you know these two
default transformations are provided by
angular thank you for listening and have
a great day
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