Map (Foundation class) consist of a data set that contains a key and a corresponding value, where the key is unique. The key and the value need not be from the same data type.
A Map is alway sorted on the key value.
Contents [hide]
1 How to use
1.1 Define
1.2 Insert a value
1.3 Exists value
1.4 Getting values
1.4.1 MapIterator
1.4.2 MapEnumerator
1.4.3 Direct method
1.5 Removing values
1.6 Updating values
1.7 Other methods
2 See also
How to use
Define
Map m = new Map(Types::STRING, Types::INTEGER); Insert a value
m.insert("Wassini", 37);
m.insert("Eric", 102); Exists value
To see if a value already is added, use the exists method:
if (m.exists("Wassini"))
print "Yes!";
else
print "No!"; Getting values
There are several ways to get the values in the map.
Using a MapIterator
Using a direct method
MapIterator
The MapIterator loops throug the complete map:
MapIterator mi;
mi = new MapIterator(m);
while (mi.more())
{
print mi.key();
print mi.value();
mi.next();
} MapEnumerator
MapEnumerator class is like MapIterator class, but allows the deletion of elements during enumeration and MapIterator does not.
MapEnumerator me = m.getEnumerator();
while (me.moveNext())
{
print me.currentKey();
print me.currentValue();
} Direct method
It is possible to get find a specific value from the key:
print m.lookup("Wassini"); Removing values
Just use the remove method to remove the active key/value pair.
m.remove("Wassini"); Updating values
It is not possible to update a value directly:
int age;
str keyid = "Wassini";
age = m.exists(keyid) ? m.lookup(keyid) : 0;
m.insert(keyid, age + 1); Other methods
// Get number of elements:
print m.elements();
// Get the used types:
print m.definitionString();
// Dump the whole map as a string:
print m.toString();
1 comment:
Map is a very useful class which basically keeps objects which the types of them determined in initialization. Map keeps two variables for each object, key and value.
Map map = new Map(Types::String, Types::Integer);
MapEnumerator mapEnumerator;
Set set;
container con;
;
map.insert('paper', 35); // Map = ['paper' -> 35]
map.insert('cup', 1500); // Map = ['cup' -> 1500, 'paper' -> 35] (It will automatically put ascending order according to keys)
map.insert('paper', 75); // Map = ['cup' -> 1500, 'paper' -> 75] (It will automatically replaces value, if key already exists in the map)
map.insert('knife', 3.4); // Map = ['cup' -> 1500, 'knife' -> 3, 'paper' -> 75] (It will automatically work to convert key/value to the type which is determined in initialization (if it could not convert, it will throw error))
print map.elements(); // prints count of elements in map which is 3
print map.exists('cup'); // prints "true" which means key 'cup' exists in map
print map.empty(); // prints "false" which means map is not empty (ie. there is at least one element in it)
set = map.keySet(); // fills set with the keys of map ['cup', 'knife', 'paper']
print map.keyType(); // prints "String" which is the type of key of map
print map.lookup('paper'); // prints 75 which is the value of the key 'paper'
con = map.pack(); // map keys and values are packed into container
map = null; // resets the map
map = map::create(con); // map is recovered from packed container
//print map.lookup('pencil'); // throws error 'The value "pencil" is not found in the map.'. So lookup method must be called after checking if key exists in the map
mapEnumerator = map.getEnumerator(); // enumerator is initialized with map
while (mapEnumerator.moveNext()) // statement will loop until mapEnumerator reaches end of map
{
print mapEnumerator.currentKey(); // prints current key
print mapEnumerator.current(); // prints current key (same as calling currentKey)
print mapEnumerator.currentValue(); // prints current value
}
pause;
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