Map is a collection of unordered key-value pairs. The most important point of Map is passing the key to retrieve data quickly key , similar to an index, points to the value of the data.
You can use built-in functions If you don’t initialize The following example demonstrates the creation and use of The running result of the above instance is as follows: The running result of the above instance is as follows: Map is a collection, so we can iterate over it like arrays and slices. But, Map is unordered, and we cannot determine the order in which it isreturned, because Map is to use the hash table to achieve. 2.39.1. Define Map #
make , you can also use the map keyword to define Map :/* Declare variables, default map is nil */ var map_variable map[key_data_type]value_data_type /* Using the make function */ map_variable := make(map[key_data_type]value_data_type)
map then a nil map . nil map cannot be used to store key-value pairs 2.39.2. Example #
map :Example #
package main import "fmt" func main() { var countryCapitalMap map[string]string /*Create Collection */ countryCapitalMap = make(map[string]string) /* Insert key value pairs into the map, corresponding to the capital cities of each country */ countryCapitalMap [ "France" ] = "Paris" countryCapitalMap [ "Italy" ] = "Rome" countryCapitalMap [ "Japan" ] = "Tokyo" countryCapitalMap [ "India " ] = "New Delhi" /*Use the key to output map values */ for country := range countryCapitalMap { fmt.Println(country, "The capital is", countryCapitalMap [country]) } /*Check if the element exists in the collection */ capital, ok := countryCapitalMap [ "American" ] /*If it is determined to be true, then it exists; otherwise, it does not exist */ /*fmt.Println(capital) */ /*fmt.Println(ok) */ if (ok) { fmt.Println("The capital of America is", capital) } else { fmt.Println("The capital city of America does not exist") } }
The capital of France is Paris Italy's capital is Rome The capital of Japan is Tokyo India's capital is New Delhi The capital city of America does not exist
2.39.3.
delete() function # delete() function is used to delete the elements of the collection, and the argument is map and its corresponding key . Examples are as follows:Example #
package main import "fmt" func main() { /* Create a map */ countryCapitalMap := map[string]string{"France": "Paris", "Italy": "Rome", "Japan": "Tokyo", "India": "New delhi"} fmt.Println("Original Map") /* Print Map */ for country := range countryCapitalMap { fmt.Println(country, "The capital is", countryCapitalMap [ country ]) } /*Delete Element*/ delete(countryCapitalMap, "France") fmt.Println("French entry deleted") fmt.Println("Map after deleting elements") /*Print Map*/ for country := range countryCapitalMap { fmt.Println(country, "The capital is", countryCapitalMap [ country ]) } }
Original map The capital of India is New delhi The capital of France is Paris Italy's capital is Rome Japan's capital is Tokyo French entry deleted Map after deleting elements Italy's capital is Rome Japan's capital is Tokyo The capital of India is New delhi