A map is an unordered and changeable collection of key-value pairs. The map data structure is used for fast lookups, retrieval, and deletion of data based on keys. It is one of the most picked data structures in computer science.
It maps keys to values. The keys are unique identifiers within a map, while the values may not be. A map key can have the data type for which the equality operator (==) is defined. The data types are:
- Arrays
- Booleans
- Numbers
- Strings
- Pointers
- Structs
Types such as Slices, Maps and Functions are invalid as equality operator (==) is not defined for them. Go provides a built-in map type with a default value of nil. This article will educate you how to use Golang’s built-in map type.
How to Create Maps in Golang?
-
Using the Map Literal:
Map with key-value pair
Syntax:
map[Key_Type]Value_Type{key1: value1, ..., keyN: valueN}
-
Using Make Function
A map can also be created by passing the type of key and value to the make() function. It is an inbuilt function. With the following syntax, we can create a new map.
Syntax:
make(map[type of key]type of value)
Creating an Empty Map
We can create an empty map by following two ways. One is by using the make() function and the other by using the map literal.
The zero or default value of a map is nil. A run-time panic will occur if you try to add elements to a nil map. Hence the map has to be initialized before adding elements. As we already know, the make() function always returns an initialized map. So we can add value to it.
How to Iterate Over a Map?
Using the range for loop, we can iterate over a map. The values printed through the loop may vary because the map is an unordered collection.
Accessing Map Elements
We can access the map elements with the following syntax.
Syntax:
value = map_name[key]
Updating and Adding Map Elements
We can update and add the map elements with the following syntax.
Syntax:
map_name[key] = value
Remove Element from Map
We can remove the map elements using the delete() function.
Syntax:
delete(map_name, key)
Check for Specific Elements in a Map
We can check if a certain key exists in a map with the following syntax.
Syntax:
val, ok :=map_name[key]
We can use the blank identifier (_) in place of val, to check the existence of a certain key.
Maps Are Reference Types
Maps are reference types. When you assign a map to a new variable, both refer to the same underlying data structure. The changes done by one variable will affect the content of the other.
Length of Map
We can find the length of a map using the len() function. The len() function calculates the number of elements in a map.
Maps Equality
Maps can be compared by checking each one's individual elements one by one. It can't be compared using the == operator. The == operator only works to check if a map is nil.
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Conclusion
In this tutorial, we learned how to create and initialize and declare maps, how to create an Empty Map, how to iterate over a Map, how to access map elements, how to update and add map elements, remove elements from map and a lot more operations of Map. This article is comprehensive, covering all the key topics relating to Map in Golang.
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