What is set in Swift?
Arrays are ordered collections of values. Sets are unordered collections of unique values. Dictionaries are unordered collections of key-value associations. Arrays, sets, and dictionaries in Swift are always clear about the types of values and keys that they can store.
What is compactMap in Swift?
The compactMap() method lets us transform the elements of an array just like map() does, except once the transformation completes an extra step happens: all optionals get unwrapped, and any nil values get discarded.
How do you automate a shell script?
To customise a shell script, we first need to create it as follows:
- To hold a text program, we need to create a text file.
- Choose a shell to write the script.
- Add the necessary commands to the file.
- Save the file.
- Change its permissions to make the file executable.
- Run the shell program.
How do I know my current shell?
Use the following Linux or Unix commands:
- ps -p $$ – Display your current shell name reliably.
- echo “$SHELL” – Print the shell for the current user but not necessarily the shell that is running at the movement.
What is reduce in Swift?
Use reduce to combine all items in a collection to create a single new value. The reduce method takes two values, an initial value and a combine closure. For example, to add the values of an array to an initial value of 10.0: let items = [2.0,4.0,5.0,7.0] let total = items.
What is for loop in Swift?
For-In Loops. You use the for – in loop to iterate over a sequence, such as items in an array, ranges of numbers, or characters in a string. This example uses a for – in loop to iterate over the items in an array: let names = [“Anna”, “Alex”, “Brian”, “Jack”]
Are sets ordered Swift?
Swift does not have a native ordered set type. If you use Foundation , you can use NSOrderedSet in Swift. If not, you have the opportunity to write your own ordered set data structure. It wraps both an array and a set and manages access to get ordered set behavior.
Is Shell Scripting easy to learn?
Well, with a good understanding of Computer Science, the so-called “practical programming” is not that difficult to learn. Bash programming is very simple. You should be learning languages like C and so forth; shell programming is rather trivial compared to these.
Which one is faster array or set in Swift?
Testing whether an object is contained in a set is faster than testing for membership of an array. As it is a static collection type it will not be possible to add or remove objects after initialization. This might be an important reason to go for an Array instead.
What is Array give the example?
An array is a data structure that contains a group of elements. Typically these elements are all of the same data type, such as an integer or string. Arrays are commonly used in computer programs to organize data so that a related set of values can be easily sorted or searched.
What is HashMap in Swift?
As a Swift developer, you’re familiar with the Dictionary structure. If you’re also a Kotlin developer, you would be familiar with the HashMap class. The underlying data structure that powers both of these constructs is the hash table data structure. The Swift dictionary is a collection of key-value pairs.
What is tuples in Swift?
Tuples in Swift occupy the space between dictionaries and structures: they hold very specific types of data (like a struct) but can be created on the fly (like dictionaries). They are commonly used to return multiple values from a function call.
What is Flatmap in Swift?
Flatmap is used to flatten a collection of collections . But before flattening the collection, we can apply map to each elements. Apple docs says: Returns an array containing the concatenated results of calling the given transformation with each element of this sequence.
How do you automate commands in Unix?
Here are my steps, in order:
- launch putty, choose hostname & port, click Open (would love to script/automate this 1st part too)
- linux shell/terminal opens.
- I enter my login and pwd.
- I enter this command: sudo su – psoftXXX.
- I enter my pwd again and hit enter.
- I am presented with a little cmd-shell menu and a prompt.
- cd /
Do try catch Swift?
The try/catch syntax was added in Swift 2.0 to make exception handling clearer and safer. It’s made up of three parts: do starts a block of code that might fail, catch is where execution gets transferred if any errors occur, and any function calls that might fail need to be called using try .
What is @escaping in Swift?
A closure is said to escape a function when the closure is passed as an argument to the function, but is called after the function returns. When you declare a function that takes a closure as one of its parameters, you can write @escaping before the parameter’s type to indicate that the closure is allowed to escape.
What is array in Swift?
Specifically, you use the Array type to hold elements of a single type, the array’s Element type. An array can store any kind of elements—from integers to strings to classes. Swift makes it easy to create arrays in your code using an array literal: simply surround a comma-separated list of values with square brackets.
What is hashable in Swift?
When we refer to the Hashable protocol documentation page, we find out that the definition of Hashable is that: “A type that can be hashed into a Hasher to produce an integer hash value.” The definition is very clear, and we can identify three keywords in this definition: type, Hasher, and integer.
What does R mean in Linux?
-r, –recursive Read all files under each directory, recursively, following symbolic links only if they are on the command line. This is equivalent to the -d recurse option.
What will $3 mean in a shell script?
Definition: A child process is a subprocess launched by another process, its parent. Positional parameters. Arguments passed to the script from the command line [1] : $0, $1, $2, $3 . . . $0 is the name of the script itself, $1 is the first argument, $2 the second, $3 the third, and so forth.
Why do we use closures in Swift?
Closures are self-contained blocks of functionality that can be passed around and used in your code. Functions and closures are first-class objects in Swift: you can store them, pass them as arguments to functions, and treat them as you would any other value or object.
How do you write a for loop in Swift?
A for loop in Swift always has the for and in keywords. The for loop then takes a sequence, items in the example above, and loops over the sequence one-by-one. With the syntax above, every item is available as the constant item within the loop. The code that’s repeated is within the squiggly brackets { } .
What is $0 and $1 in Swift?
$0 and $1 are Closure’s first and second shorthand arguments (a.k.a. Shorthand Argument Names or SAN for short). The shorthand argument names are automatically provided by Swift. The first argument can be referenced by $0 , the second argument can be referenced by $1 , the third one by $2 , and so on.
What is a for in loop?
A “For” Loop is used to repeat a specific block of code a known number of times. For example, if we want to check the grade of every student in the class, we loop from 1 to that number.
What is Nsdictionary in Swift?
An object representing a static collection of key-value pairs, for use instead of a Dictionary constant in cases that require reference semantics.
What is $1 in Linux?
$1 is the first command-line argument passed to the shell script. $0 is the name of the script itself (script.sh) $1 is the first argument (filename1) $2 is the second argument (dir1)
What is $? In Unix?
$? -The exit status of the last command executed. $0 -The filename of the current script. $# -The number of arguments supplied to a script. $$ -The process number of the current shell. For shell scripts, this is the process ID under which they are executing.
What is $0 shell?
$0 Expands to the name of the shell or shell script. This is set at shell initialization. If Bash is invoked with a file of commands (see Section 3.8 [Shell Scripts], page 39), $0 is set to the name of that file.