66 lines
1.7 KiB
Markdown
66 lines
1.7 KiB
Markdown
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---
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title: Go Maps
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---
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## Go Maps
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A map, called a _dictionary_ in other languages, "maps" keys to values.
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A map is declared like this:
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```go
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var m map[Key]Value
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```
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This map has no keys and no keys can be added to it.
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To create a map, use the `make` function:
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```go
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m = make(map[Key]Value)
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```
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Anything can be used as a key or as a value.
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### Modifying maps
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Here are some common action with maps.
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#### Inserting/Changing elements
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Create or change element `foo` in map `m`:
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```go
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m["foo"] = bar
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```
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#### Getting elements
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Get element with key `foo` in map `m`:
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```go
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element = m["foo"]
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```
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#### Deleting elements
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Delete element with key `foo` in map `m`:
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```go
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delete(m, "foo")
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```
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#### Check if a key has been used
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Check if key `foo` has been used in map `m`:
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```go
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element, ok = m["foo"]
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```
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If `ok` is `true`, the key has been used and `element` holds the value at `m["foo"]`.
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If `ok` is `false`, the key has not been used and `element` holds its zero-values.
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### Map literals
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You can directly create map literals:
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```go
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var m = map[string]bool{
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"Go": true,
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"JavaScript":false,
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}
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m["Go"] // true
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m["JavaScript"] = true // Set Javascript to true
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delete(m, "JavaScript") // Delete "JavaScript" key and value
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language, ok = m["C++"] // ok is false, language is bool's zero-value (false)
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```
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#### More Information:
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<!-- Please add any articles you think might be helpful to read before writing the article -->
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* [A Tour of Go](https://tour.golang.org/moretypes/19)
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* [Go By Example](https://gobyexample.com/maps)
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* [Golang Book](https://www.golang-book.com/books/intro/6#section3)
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* [The Go Programming Language Specification](https://golang.org/ref/spec#Making_slices_maps_and_channels)
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