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Navigation: Code Documentation > RSCommon > RSGenerics.Collections > Classes

TRSDictionary<TKey,TValue> Class

Collection of key-value pairs.

TRSDictionary represents a generic collection of key-value pairs.

This class provides a mapping from a collection of keys to a collection of values. When you create a TRSDictionary object, you can specify various combinations of initial capacity, equality operation, and initial content.

You can add a key that is associated with a corresponding value with the Add or AddOrSetValue methods. You can remove entries with Remove or Clear, which removes all key-value pairs. Adding or removing a key-value pair and looking up a key are efficient, close to O(1), because keys are hashed. A key must not be nil (though a value may be nil) and there must be an equality comparison operation for keys.

You can test for the presence or keys and values with the TryGetValue, ContainsKey and ContainsValue methods.

The Items property lists all Count dictionary entries. You can also set and get values by indexing the Items property. Setting the value this way overwrites any existing value.

note Note

The TRSDictionary<TKey,TValue> class was created to address problems in the TDictionary class that prevented subclassing from the class. The TRSHashTable<TKey,TValue> needed some changes (as of XE4) in order to properly mimic the older TGHashTable class from RiverSoftAVG:

• moved FItems to protected

• moved DoAdd to protected and made it virtual

• moved DoSetValue to protected and made it virtual

• moved DoRemove to protected and made it virtual

• Changed Remove from procedure to function

Namespace: RSGenerics.Collections

Type Parameters

TKey

TValue

	Name	Description
	Create(IEqualityComparer)	Overloaded. Creates and initializes the dictionary.
	Create(Integer)	Overloaded. Creates and initializes the dictionary.
	Create(Integer,IEqualityComparer)	Overloaded. Creates and initializes the dictionary.
	Create(TEnumerable)	Overloaded. Creates and initializes the dictionary.
	Create(TEnumerable,IEqualityComparer)	Overloaded. Creates and initializes the dictionary.
	Destroy	Represents the destructor of the TRSDictionary<TKey,TValue> class.

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	Name	Description
	Count	Number of entries. Count holds the number of key-value pairs in the dictionary. The Items property holds Count entries.
	Items[TKey]	Indexable list of all dictionary entries. Items is an indexable list of all key-value pairs in the dictionary. The Count property holds the number of dictionary entries in Items. You can set and get values by indexing the Items property. Setting the value this way overwrites an existing value and does not raise an exception.
	Keys	Indexable list of all dictionary keys. Keys is a read-only enumerable collection of all keys in the dictionary. The Count property holds the number of entries in Keys.
	OnKeyNotify	Occurs when a dictionary key pair changes. The OnKeyNotify event occurs when items are added or removed from the dictionary. Multiple events may occur for a single operation. This allows removed objects to be freed.
	OnValueNotify	Occurs when a dictionary key pair changes. The OnValueNotify event occurs when items are added or removed from the dictionary. Multiple events may occur for a single operation. This allows removed objects to be freed.
	Values	Indexable list of all dictionary values. Values is a read-only enumerable collection of all values in the dictionary. The Count property holds the number of entries in Values.

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	Name	Description
	Add(TKey,TValue)	Add key-value pair. Add adds a key and its corresponding value to the dictionary. Both the key and the value can be nil. If the key already exists in the dictionary, an exception is thrown. An OnKeyNotify event and an OnValueNotify event occur indicating that an entry was added to the dictionary. The Items property lists all dictionary entries. You can also set and get values by indexing directly the Items property. For instance, you can set a value this way: Delphi
Items[key] := value;

Setting the value this way overwrites the value for an existing key, but does not raise an exception.

public method

AddOrSetValue(TKey,TValue)

Add key-value pair even when key already exists.

AddOrSetValue adds a key-value pair to a dictionary even if the key already exists. The key cannot be nil, but the value can. This method checks to see if the key exists in the dictionary, and if it does, it is equivalent to Items[key] := value;. Otherwise it is equivalent to Add(key, value);.

An OnKeyNotify event and an OnValueNotify event occur indicating an entry was added to the dictionary.

public method

Assign(TPersistent)

Copies the source dictionary to the current dictionary. The current dictionary is cleared first.

public method

Clear

Clear all data.

Clear removes all keys and values from the dictionary. The Count property is set to 0. The capacity is also set to 0. This operation requires O(n) time, where n is Count, the number of dictionary entries.

Note
Clear does not free the items as they are removed. If you need to free them, use the OnKeyNotify event and the OnValueNotify event, which occur for every entry removed and provides the removed items.

public method

ContainsKey(TKey)

Test if key in dictionary.

ContainsKey returns true if the given key is in the dictionary and false otherwise. This is an O(1) operation.

public method

ContainsValue(TValue)

Check if value in dictionary.

ContainsValue returns true if the given value is in the dictionary and false otherwise. This is an O(n) operation, where n is the number of entries in the dictionary.

protected method

DoAdd(Integer,Integer,TKey,TValue)

Adds key/value pair to dictionary at the given index

protected method

DoGetEnumerator

Returns the container's enumerator.
(Overrides RSGenerics.Collections.TRSEnumerable<T>.DoGetEnumerator.)

protected method

DoRemove(TKey,Integer,TCollectionNotification)

Removes key/value pair from dictionary

protected method

DoSetValue(Integer,TValue)

Overwrites value in dictionary at the given index

public method

ExtractPair(TKey)

Returns the TPair<TKey,TValue> pair with the specified Key and removes the returned pair from a dictionary.

If the dictionary does not contain the specified Key, the returned pair contains a default TValue.

public method

GetEnumerator

Returns an key-value pair enumerator for the dictionary.

protected method

KeyNotify(TKey,TCollectionNotification)

Triggers an OnKeyNotify event with the given parameters.

Call KeyNotify to trigger an OnKeyNotify event with the given parameters.

The meaning of the parameters is given in the following table:

Key

The key that is added, removed or extracted.

Action

The action that the key undergoes, which is of type TCollectionNotification.

public method

Remove(TKey)

Remove key-value pair.

Remove removes the given key and its associated value from the dictionary. No exception is thrown if the key is not in the dictionary. This is an O(1) operation.

An OnKeyNotify event and an OnValueNotify event occur indicating an entry was removed from the dictionary.

public method

ToArray

Returns the content of the dictionary as an array.
(Overrides RSGenerics.Collections.TRSEnumerable<T>.ToArray.)

protected method

ToArrayImpl(Integer)

Converts the enumerable container's items into an equivalent TArray of items. (Inherited from RSGenerics.Collections.TRSEnumerable<T>.)

public method

TrimExcess

Reduce capacity to current number of entries.

TrimExcess changes the capacity to the number of dictionary entries, held in Count.

This method rehashes the internal hash table to save space. This is only useful after a lot of items have been deleted from the dictionary.

public method

TryGetValue(TKey,TValue)

Try to get value for key.

TryGetValue returns true if the given key is in the dictionary and provides its value in Value. Otherwise, it returns false and Value is set to the default value type of TValue. No exception is raised if the key is not in the dictionary. This is an O(1) operation.

protected method

ValueNotify(TValue,TCollectionNotification)

Triggers an OnValueNotify event with the given parameters.

Call ValueNotify to trigger an OnValueNotify event with the given parameters.

The meaning of the parameters is given in the following table:

Value

The Value that is added, removed or extracted.

Action

The action that the Value undergoes, which is of type TCollectionNotification.

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