Udacity Networking in iOS and Swift

Question 1

What is a singleton?

Answer 1

A singleton is an special kind of object that can only be instantiated once. So if you use the shared URLSession in this file, and then in a another file you use the shared URL session, you’re actually still referring to the same object in both files, becuase it’s a singleton there can only be one.

Question 2

What is a completion handler?

Answer 2

A completion handler is a block of code that is executed after something completes like a network task

Question 3

What is ATS?

Answer 3

App Transport Security - ATS

Apple’s set of security standards for ensuring our apps keep users’ data safe.

Question 4

What is URL in Swift?

Answer 4

URL represents a URL

Question 5

What is URLSession ?

Answer 5

URLSession manages network requests for our app

Question 6

What is URLSessionConfiguration ?

Answer 6

URLSessionConfiguration specifies settings (eg timeout interval) for a NSURLSession (or URLSession?)

Question 7

What is URLSessionTask ?

Answer 7

URLSessionTask is a network task that can be executed

Question 8

What is URLSessionDataTask ?

Answer 8

URLSessionDataTask is a subclass of NSURLSessionTask; it downloads data directly into memory

Question 9

What is URLSessionDownloadTask ?

Answer 9

URLSessionDownloadTask is a subclass of NSURLSessionTask; it downloads data temporary file

Question 10

What is URLSessionUploadTask ?

Answer 10

URLSessionUploadTask is a subclass of NSURLSessionTask; it is specialsed for uploading data

Question 11

What is URLResponse ?

Answer 11

URLResponse is a container for information about the response to a network request such its status code

Question 12

What is Error ?

Answer 12

Error is a container for information about an error condition

Question 13

What are the steps for getting JSON data and parsing it?

Answer 13

1. Get the raw JSON data.
2. Parse the JSON data into a foundation object, like an NS dictionary, or an NSArray.
3. Grab the data from the Foundation object.

Question 14

Describe deserialising JSON?

Answer 14

• get photos dictionary at the “photos” key
• in the photos dictionary, get the array of the photo dictionaries at the “photo” key
• print the first photo dictionary

if let photosDictionary = parsedResult[Constants.FlickrResponseKeys.Photos] as? [String:AnyObject], let photoArray = photosDictionary[Constants.FlickrResponseKeys.Photo] as? [[String:AnyObject]] {
                        print(photoArray[0])

Question 15

In terms of URLComponents, break down the structure of a web address and building it

Answer 15

Note we do this because the URLComponents class ensure that all characters are escaped and URL contains only safe ascii characters

The URL:
https://api.flickr.com/services/rest?
method=flickr.photos.search&
api_key=980958230459843086554&
text=purple

First line: :// / (to ?)

everything after the ? is the query

They consist of name: value pairs that a server uses to determine its response -
eg
text=purple
method=method=flickr.photos.search&amp
These are name=value. Each pair is separated by an &

To add the query line (eg after the ? to the end), we need to add a URLQueryItem (see below), add the key : value pairs, and then append them to the component var (aka the URL)

var components = URLComponents()

components. scheme = “https”
components. host = “api.flickr.com”
components. path = “/services/rest”
components. queryItems = URLQueryItem

let queryItem1 = URLQueryItem(name: "method", value: "flickr.photos.search")
let queryItem2 = URLQueryItem(name: "api_key", value: "1234")
let queryItem3 = URLQueryItem(name: "text", value: "purple")

components. queryItems!.append(queryItem1)
components. queryItems!.append(queryItem2)
components. queryItems!.append(queryItem3)

print(components.url!)

Question 16

Network

Answer 16

Network — the system of interconnected computer networks from which we can access data.

Question 17

Data

Answer 17

Data — images, text, video, or any media that can be used by our apps.

Question 18

Protocol

Answer 18

Protocol — a way of communicating; standard operating procedure; the rules for communication

Question 19

HTTP

Answer 19

HTTP (Hypertext Transfer Protocol) — a protocol or “handshake” that defines how messages (and data) are sent and received by computers; the underlying protocol for the World Wide We

Question 20

Client

Answer 20

Client — a computer that requests data (or services) from a server

Question 21

Server

Answer 21

Server — a computer that provides data (or services) to a client upon request

Question 22

HTTP request

Answer 22

HTTP request — a request for data (or a resource) that a client makes to a server; there are various types of HTTP requests called “HTTP methods”

Question 23

URL

Answer 23

URL (Uniform Resource Locator) — specifies the location for retrieving data over the web; can be thought of as the name of a file on the World Wide Web, because it usually refers to a file on some machine on the network

Question 24

HTTP method

Answer 24

HTTP method — specifies the type of HTTP request that is being made; in this course, we will also called these (HTTP) request types

Question 25

HTTP status code

Answer 25

HTTP status code — a number returned in response to an HTTP request which indicates the result of the request; you may also hear these referred to as “response codes” or “status messages”; here is a nice listing of different HTTP status codes

Question 26

HTTP GET request

Answer 26

HTTP GET request — a type of HTTP request where a client requests a specified resource from a server

Question 27

Completion handler

Answer 27

Completion handler — a block of code that is executed after something completes like a network task

Question 28

HTTPS

Answer 28

HTTPS — a protocol built on top of HTTP that ensures data sent over the network is encrypted, or concealed, from unauthorized access

Question 29

ATS

Answer 29

ATS (App Transport Security) — Apple’s set of security standards for ensuring our apps keep users’ data safe

Question 30

Singleton

Answer 30

Singleton — a special kind of object that can only be instantiated once

Question 31

URL

Answer 31

URL — represents a URL

Question 32

URLSession — manages network requests for our app

Answer 32

URLSession — manages network requests for our app

Question 33

URLSessionConfiguration

Answer 33

URLSessionConfiguration — specify settings (ex. timeout interval) for a NSURLSession

Question 34

URLSessionTask

Answer 34

URLSessionTask — a network task that can be executed

Question 35

URLSessionDataTask

Answer 35

URLSessionDataTask — subclass of NSURLSessionTask; downloads data directly into memory

Question 36

URLSessionDownloadTask

Answer 36

URLSessionDownloadTask — subclass of NSURLSessionTask; downloads data to a temporary file

Question 37

URLSessionUploadTask

Answer 37

URLSessionUploadTask — subclass of NSURLSessionTask; specialized for uploading data

Question 38

Data

Answer 38

Data — represents data as raw bytes

Question 39

URLResponse

Answer 39

URLResponse — a container for information about the response to a network request such its status code

Question 40

Error

Answer 40

Error — a container for information about an error condition