Go Maps
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Internal
Overview
A map is an unordered collection of key-value pairs.
Declaration
Long Declaration
var map_identifier map[key_type]value_type
Example of a map of string to ints:
var m map[string]int
Note that maps must be initialized before attempting to write into them, see Assinging a Value to an Unitialized Map.
Declaration and initialization:
var m map[string]string = make(map[string]string)
Short Declaration
m := make(map[string]string)
Short Declaration
Map Operators and Functions
Indexing Operator
Indexing operator [] returns the value corresponding to the specified key. If the key does not exist, the zero value for the value type is returned.
Assigning a Value to an Uninitialized Map
If the indexing operator is also used to assign a value to a key for an uninitialized map, we get a runtime error:
panic: assignment to entry in nil map