LEARN GOLANG| Part-2

In this blog, we shall be looking at following concepts :-

  • Concept of Arrays in GoLang.

Question:- Can you demonstrate the usage of Arrays in GoLang ?

  • We have declared an Array of Strings at line #8. This is an Array of 4 Strings have been initialised.

Question:- Given the fact that, we have defined the array of fixed size, what would happen, if we add value to the index, which has not been declared

Answer:- We shall land into OutOfBounds situation, as we try to add the value to the Index, which doesn’t exists at all. This is one of the shortcoming of the fixed size Array.

Question:- Can we perform the Sorting on the Arrays ?

Answer:- No again, this is yet another issue with the Arrays. We can’t perform the sorting operation on the Arrays.

Question:- What’s the alternative ? How can we make it possible that, we can add unlimited entries to the Array ?

Answer:- This is possible with SLICE. Here is an example for the same :-

  • Note that, at line #14, we are trying to add more entries tot he Array earlier declared. And we can add infinite elements, there is no constraint of size here.

Question:- Explain concept of Slices with GO program ?

Answer:- Slices are built on top of Arrays. Slices are powerful way of dealing with Array based Operations in Go :-

  • At line #26, We are iterating over the elements in the slice, you can use the conditional for loop. We start with zero, up to the length of the loons, and then i++, print the loon.

Question:- Demonstrate the Unordered Map with Go-Lang ?

Answer:- In Go-Lang, we have an unordered collection of elements called Map :-

  • Note that, we are using make() function at line #8, in order to initialise the Map.

Question:- Demonstrate how can we iterate through the Unordered Map in Go-Lang ?

Answer:- While, we iterate through Map, order is not guaranteed. Here is how we can iterate through the Map :-

Question:- How do we print the entries (K,V) pair from the MAP in ordered way ?

Answer:- We can first take the keys from the map, sort them and then basis of keys, we can print the entries from the Map :-

Note here that, at Line #15, we are making use of the Slices. This is one special variety of Unbounded Array, which can grow as much as we want.

Question:- Explain concept of Maps with GO program ?

Answer:- Maps are well supported in Go, where we can house <K,V> pairs of varied types :-

Example:- Demonstrate counting of words along with their frequency using GO program ?

Question :- How do we declare any function in the GoLang ?

Question:- Demonstrate the concept of Functions with GO program ?

Answer:-

  • Functions in GO can very well return multiple values too.

Question:- Let’s now demonstrate usage of functions in Go-Lang ?

Answer:- We shall be defining the function, which would perform ADD operation on two integer type numbers :-

Question:- How can we define the method, which can take unknown number of variables in request and perform some action in function in Go-Lang ?

Answer:- We shall be defining the method in below fashion :-

  • This method can receive infinite values in input.

Remember that, in case we want, even we can just skip the index very well by using _ (underscore) character. In below case, we shall not have any need to even make use of the Index :-

Question:- How can we define the method, which can return multiple values?

Answer:- We shall be defining the method in below fashion, which would be returning the multiple values :-

Question:- How can we define the functions as method of custom types?

Answer:-

  • Here In Go-Lang, we can attach functions to your custom types. They’re then referred to as methods.

Question:- Does methods work on CallByReference OR CallByValue?

Answer:- Within the function at line #21, I’m reassigning the value of the sound field.

  • So what do we think is going to happen? Will the dog bark three times, or nine times? And the answer is that it only barks three times.

Question:- Demonstrate the value passing to Functions with GO program ?

Very Important Concepts→ At line # 21, we have defined a function : double(val) → We see that the original value hasn’t changed.

  • Call by ValueWhen Go passes an integer to a function, Go passes it by value which means, Go will create a copy of this integer and pass it to the function. Any changes to the integer inside the function won’t affect the original value.

Question:- Does GO support usage of pointers ?

Answer:- Yes, GO supports the use of pointers. These are variables that store the memory address of another variable.

Question:- Can you demonstrate the usage of pointer ?

Answer:-

  • Demo #1 Here, *int indicates that, thisVar is a pointer and not value. And if I don’t assign anything, that means that, variable will be nil; it doesn’t contain anything.
  • Demo #2 Here, we are printing the *thisVar, which indicates that, thisVar is a pointer and not value. This time, it throws the RuntimeError indicating the InvalidMemoryAddress.

Question:- Can you demonstrate, how a particular variable can refer to the address of another variable ?

  • Here, variable “thisParticularInVar” is valued at 75.

Question:- If we try to manipulate the value of a variable through it’s pointer, then whether the actual value of the variable shall also be changed ?

  • Notice that, at line #8, we specifically want the type of the variable to be inferred. Here, we want that GO-compiler should be auto-inferring the type of 75.

Question:- Demonstrate the usage of Pointers for Objects, in GO ?

Answer:- Here below code-piece :-

  • At line #21, the variable “p” houses the address of an object (which is of type “Point”).

Question:- How can you make method work, with plain values in GO ?

Answer:- You can do this by using pointers. If you’re coming from C or C++, the word pointer might be associated with obscure code and crashes. Don’t worry, Go’s pointers are not like C or C++. They are much safer.

Demonstration:- Let’s showcase an example of nested objects with their methods exposed :-

Solution:- Here, we are showcasing the Square shape with nested object of Point in it :-

Step #1.) Let’s first create a Point struct :-

Step #2.) Let’s now write up a method Move, to showcase the movement of Point :-

Step #3.) Let’s now create a Square struct :-

Step #4.) Let’s now write up methods : Move & Area, to showcase the movement of Square AND calculate the area of Square :-

Step #5.) Let’s now create constructor for our struct Square:-

Step #6.) Let’s test the functionality by invoking the afore-written methods :-

Question:- Demonstrate the concept of Interfaces with GoLang ?

Usecase:- You have some shapes defined, like square and circle. Both the square and the circle, we find an area method. Now we’d like to write the function that receives a slice of shapes and return the sum of the areas.

Concept) What’s an Interface ?

Answer:- An interface is a collection of methods, and each type, it implements all the methods in the interface. Interfaces are a very useful abstraction and you’ll see them a lot. For example, the io.reader and io.Writer from the I/O package, define something you can read from and something you can write to. With these interfaces, you can use the same code to read from files, socket, compressed files, hash signatures, and more.

Demo Step #1.) Let’s first mention the packages that we shall be importing :-

Demo Step #2.) Next let’s create an Interface named “Shape” :-

Demo Step #3.) Next let’s create an struct (i.e. custom structure / POJO) with name “Square” :-

Demo Step #4.) Next let’s create a method “Area()” in order to compute the area of Square :-

Demo Step #5.) Next let’s create an another struct (i.e. custom structure / POJO) with name “Circle” :-

Demo Step 6.) Next let’s create a method “Area()” in order to compute the area of Circle :-

Demo Step 7.) Next let’s create the method “sumAreas()” in order to compute the sum of areas of all shapes received :-

Note that, we are receiving the slice of Shapes inside this method and in turn, we return the sum total of areas of all shapes.

Demo Step 8.) Next let’s test run this method :-

Demo Step 9.) Here is output :-

That’s all in this section. If you liked reading this blog, kindly do press on clap button multiple times, to indicate your appreciation. We would see you in next part of this series with Hands-On with Redis-Cluster.

References :-

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aditya goel

aditya goel

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Software Engineer for Big Data distributed systems