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Go from the beginning – using maps


You should have eventualities once you code that there are issues you want to search for. In the event you use a dictionary for instance you may search for how one can translate a phrase from English to Spanish or vice versa. In programming, you’ve got related conditions, perhaps you need to know what service is run on a sure port for instance. There’s additionally databases that is based mostly across the idea of getting a singular key that factors to a sure worth.

How all that is applied is through map construction. The thought is that you simply outline a key and worth and acquire all these in a bunch, a map.



Making a map

To create a map in Go, we have to use the next syntax:

map[<key type>]<worth kind>{ ... entries }
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This is an instance of making a map construction that might maintain a cellphone ebook:

phonebook := map[int]string{ 555123: "Robin Hood", 555404: "Sheriff of Nottingham"}
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We outline a map construction with key kind int and worth kind string. Then we assign it worth with {}. Every entry is outlined in accordance <key>: <worth> and separated by comma. So how can we learn a worth?



Create a map with make()

One other approach to create a map us through the use of the make() operate. make() returns a initialized map should you give it a kind like so:

dictionaryEnSv = make(map[string]string)
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Including entries

So as to add entries to the map, you want to present it with a key and worth entry like so:

dictionaryEnSv["hello"] = "hej"
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Learn a worth by key

Think about now that we now have these two entries, and also you need the worth given that you’ve then entry 555404, how would we try this? We use the sq. brackets like so []:

phonebook[555404] // "Sheriff of Nottingham"
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Examine for present entry

So that you discovered that phonebook[555404] offers you a worth again. What if it would not exist? What occurs should you give it a key that is not saved within the map is that you simply get nothing again:

phonebook[888] //
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There’s a greater approach to test this, as a result of accessing an entry with a key really returns two values, the worth, and a boolean. The boolean signifies if this key exists within the map. See this code:

_, exist phonebook[888]
fmt.Println(exist) // false
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You may even use this in an if assertion:

if _, exist := phonebook[888] {
  // quantity exist, name particular person
}
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Iterate over a map

We are able to iterate over a map with a for assemble and a vary. This is how one can iterate:

for key, worth := vary phonebook {
  fmt.Println(key, worth)
}
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Delete an entry

To take away an entry from a map, you need to use the delete() technique. The delete() technique takes the map and the important thing to delete as parameters, like so:

delete(phonebook, 555404)
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Abstract

We have discovered what a map is and when to make use of it. Moreover, we have additionally discovered learn how to create it, add values to it and browse from it, each key by key and iterating over the entire map.

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