Go Collection

Question 1

What is an Array ?

Answer 1

A collection with fixed length and similar datatype.

Question 2

What is the long syntax of declaring array in GO ?

Answer 2

var <arrayName> [<arrayLength>]<dataType>
e.g. var myArray [3]int</dataType></arrayLength></arrayName>

Question 3

How to initialise a declared array ?

Answer 3

Using the index.
e.g. myArray[1] = 12

Question 4

What is the short syntax of creating and initialisation of array in a single line ?

Answer 4

myArray := [4]int{1,2,3,4}

Question 5

What’s a slice ?

Answer 5

Slice is a collection of similar datatypes, whose length is not fixed.
It gets expand as new elements gets added and shrink as older elements gets removed.

Question 6

How to initialise an empty array ?

Answer 6

It can be initialised with empty Curly braces.
e.g. myArray := [3]int{}

Question 7

Is it mandatory to initialise variable in shorthand operator ?>

Answer 7

Yes.

Question 8

How to create an empty slice in Go ?

Answer 8

Same syntax of Array without the length.
e.g. mySlice := []int{}

Question 9

How to append a new element in existing slice ?

Answer 9

Built-in “append” function:
e.g. mySlice = append(mySlice, 23, 445)

Question 10

How to get a “slice” of an array ?

Answer 10

By providing the upper index and lower index:
e.g. mySlice := myArray[ 3:8]

Question 11

How to create slice of an array for all elements ?

Answer 11

DO NOT provide the lower and upper index
e.g. mySlice := myArray[:]

Question 12

How to create a Map in Go ?

Answer 12

Using “map” keyword and providing datatype of both “key” and “value”:
e.g. myMap := map[string]int{}

Question 13

How to initialise a Map during declaration ?

Answer 13

By Passing JSON like structure in “key” value format:
e.g. myMap := map[string]{“key”:12}

Question 14

How to get a value from Map, after providing the Key ?

Answer 14

myMap[“key”]

Question 15

How to re-assign a new Value to existing key in a map ?

Answer 15

myMap[“key”] = value

Question 16

How to delete any key-value from a Map ?

Answer 16

Using inbuilt “delete” function.
e.g. delete(myMap, “key”)

Question 17

What do you mean by “Homogeneity” of “Arrays, Slices and Maps”

Answer 17

Arrays, Slices and Maps are homogeneous, which means they can only hold similar data types.

Question 18

Which collection in Go is “heterogeneous” ?

Answer 18

Struct (just like classes, it can have any type of fields and functions)

Question 19

What is Struct ?

Answer 19

A Struct is a heterogeneous collection, which can hold data of different types.

Question 20

How to declare a “Struct” ?

Answer 20

By using “Type” and “Struct” keyword:
e.g.
type user struct {
id int,
firstName string,
lastName string
}

Question 21

How to initialise a struct ?

Answer 21

It can be initialised just like a map:
e.g. u := user{ id: 1, firstName: “Nandan”, lastName: “singh”}

Question 22

What’s a package in a module ?

Answer 22

A package is a collection of source files which shares unique responsibility within a module.

Question 23

How to import a package with module ?

Answer 23

Using “Fully qualified Name”:
e.g. import “github.com/myCompany/myRepo/myPackage”

Question 24

How to declare a function ?

Answer 24

Using “Func” keyword:
func MyFunction(){
fmt.Println(“using function”)
}

Question 25

How to invoke a function ?

Answer 25

By using “Parenthesis”
e.g. myFunction()

Question 26

How to pass arguments to any function ?

Answer 26

func myFunction( param1 int, param2 string){
fmt.Println(“Using params”, param1, param2)
}

Question 27

Do we need to provide “return Type” in Go functions ?

Answer 27

Yes

Question 28

How to provide return “data Type” in Function ?

Answer 28

After “parenthesis” and before curly braces in Function declaration:
func myFunc( param1, param2 int) int {
fmt.Println(“hey”)

}

Question 29

What is the data type required for return the exceptions in GO?

Answer 29

“error”

Question 30

How to create a new Error value ?

Answer 30

By calling the New function of “errors” package
» err := errors.New(“something bad happend”)

Question 31

How to throw an error from a function?

Answer 31

func myFunction() error {
return errors.New(“something bad happend”)
}

Question 32

Can we provide multiple return types in Go function ?

Answer 32

yes, a single function can return the multiple values.

Question 33

How to return multiple values from a function ?

Answer 33

By providing multiple “return types” separated by comma:
func myFunc() (int, error) {
return 23, nil
}

Question 34

How to consume multiple values returned by a function. ?

Answer 34

By declaring variables equals to the return values
»>
myValue, err := myFunc()

Question 35

How to consume only selected return values, if a function returns multiple values ?

Answer 35

Just declare the variable as “underscore”.
»> _ , _ := myFunction()

Question 36

Can we use “short assignment” operation outside the function ?

Answer 36

No

Question 37

How to create variable outside the function ?

Answer 37

Use Long assignment and declaration
»> var myVar int = 1

Question 38

What is a “variable” block ?

Answer 38

Multiple variable declaration collected inside the parenthesis without repeating the word “var”.
»> var (
myVar1 int
myVar2 string
)

Question 39

Can we use “increment/decrement operator” inside a statement ?

Answer 39

No, increment and decrement operators are statement in itself. Hence, it should be used in a it’s own line.
»> myNum := 1
myNum++

Question 40

Does golang support both “pre-fix” and “post-fix” increment and decrement operator ?

Answer 40

No, it only supports Post Fix, “increment” and “decrement” is supported.

Question 41

Can we add a “behaviour” to any custom data type in GO ?

Answer 41

Yes, by using Methods.

Question 42

Does Go supports class ?

Answer 42

No, Go-lang doesn’t supports classes, it only supports Types.

Question 43

What are “methods” in GO ?

Answer 43

Methods are the functions with special “receiver argument”.
This argument “binds” the function with the Type.

Question 44

How to declare a method in Go?

Answer 44

// create custom Type
type User struct { firstName, lastName string}
// create method (or behaviour)
func (user User) getFullName string {
return user.firstName + “ “ + user.lastName
}

Question 45

How to convert any function into a Method ?

Answer 45

By “Binding” it with a function.
The binding is done by “receiver argument”. It simply means, the object itself is passed to the function during runtime.

Question 46

Does Go supports constructor ?

Answer 46

No

Question 47

What’s a constructor ?

Answer 47

A constructor is a special kind of function, whose sole responsibility is to “initialise the object” when it first formed.

Question 48

What are the convention/practice needs to be followed to create a constructor function ?

Answer 48

Practice/Properties:
1. It starts with “new” word followed by the Type which it needs to initialise
2. It is always ZERO argument
3. It always returns the “type” which it initialises

Question 49

Declare a constructor function for type “user” ?

Answer 49

type User struct { firstName, lastName string }

func newUser(){
return user{ “Nandan”, “Singh”}
}

Question 50

How to start a server in Go?

Answer 50

By using the Method “ListenAndServer” method of “http” pacakge