Maps
Related Doc:
package stdlib
Attempted removal of nonexistent elements from a map is handled gracefully:
Map values can be iterated:
If a nonexistent map key is requested using myMap(missingKey), a NoSuchElementException will be thrown.
If a nonexistent map key is requested using myMap(missingKey), a NoSuchElementException will be thrown.
Default values may be provided using either getOrElse or withDefaultValue for the entire map:
Maps do not contain multiple identical pairs:
Maps insertion with duplicate key updates previous entry with subsequent value:
Maps can be added to easily:
Map elements can be removed easily:
A Map is an Iterable consisting of pairs of keys and values (also named mappings or associations).
A Map is an Iterable consisting of pairs of keys and values (also named mappings or associations). Scala's Predef class offers an implicit conversion that lets you write key -> value as an alternate syntax for the pair (key, value). For instance Map("x" -> 24, "y" -> 25, "z" -> 26) means exactly the same as Map(("x", 24), ("y", 25), ("z", 26)), but reads better.
The fundamental operations on maps are similar to those on sets. They are summarized in the following table and fall into the following categories:
apply, get, getOrElse, contains, and isDefinedAt. These turn maps into partial functions from keys to values. The fundamental lookup method for a map is: def get(key): Option[Value]. The operation "m get key" tests whether the map contains an association for the given key. If so, it returns the associated value in a Some. If no key is defined in the map, get returns None. Maps also define an apply method that returns the value associated with a given key directly, without wrapping it in an Option. If the key is not defined in the map, an exception is raised.+, ++, updated, which let you add new bindings to a map or change existing bindings.-, --, which remove bindings from a map.keys, keySet, keysIterator, values, valuesIterator, which return a map's keys and values separately in various forms.filterKeys and mapValues, which produce a new map by filtering and transforming bindings of an existing map.Maps can be created easily:
Maps may be accessed:
Map keys may be of mixed type:
Map equivalency is independent of order:
Map elements can be removed in multiple:
Map elements can be removed with a tuple:
The parameterless execute method has been deprecated and will be removed in a future version of ScalaTest. Please invoke execute with empty parens instead: execute().
The trap method is no longer needed for demos in the REPL, which now abreviates stack traces, and will be removed in a future version of ScalaTest