How +to use array keys

To access an array by key construct a TKeyArrayFix, TKeyArrayVar or TKeyArrayPak object. +The choice depends on the array type used and the member function accessed.

The following code fragments show how this is done. They construct and +manipulate an array of TBankAct objects that contain data +members representing typical bank account details.

The following code builds a CArrayFixFlat containing three +elements of type TBankAct, as follows:

Sorting the array

To sort the array into account +number order, first construct a TKeyArrayFix object to define +the location and type of key on which to sort the array:

TKeyArrayFix actNumKey(_FOFF(TBankAct,iActNum),ECmpTUint);

In practice, a data member like iActNum may be private, +in which case this statement may not be permitted by the compiler. Two solutions +are:

Make the class in which actNumKey is +declared a friend of TBankAct
Declare a public const static TInt data +member iOffset (for example) in the TBankAct class +and include a line of code:

const TInt TBankAct::iOffset += _FOFF(TBankAct,iActNum);

actNumKey can then be constructed:

TKeyArrayFix actNumKey(bankact.iOffset,ECmpTUint);

ECmpTUint is +an enumerator of the TKeyCmpNumeric enumeration; this constructor +defines a numeric key.

Now use the key definition to do the sort:

... +anArray->Sort(actNumKey); +...

See also:

_FOFF

Re-sort the array

Re-sort the array into account +name order, ignoring the case of the name, and then insert another element +into the array maintaining the same order.

First, construct another TKeyArrayFix object:

TKeyArrayFix actNameKey(_FOFF(TBankAct,iActName),ECmpFolded);

ECmpFolded is an enumerator of the TKeyCmpText enumeration; this constructor +defines a descriptor key.

Now use the key definition to re-sort the +array and insert a new element into the correct place:

... +anArray->Sort(actNameKey); +... +_LIT(KNewName,"W.B.NewPerson"); +... +bankact.iActName = KNewName; +bankact.iActNum = 69; +bankact.iActValue = 24; +... +anArray->InsertIsqL(bankact,actNameKey); +...

Note that the function InsertIsqL() does +not permit duplicates. If there is already an element with the same account +name in the array, then the call to the function leaves withKErrAlreadyExists.

Use +the key definition to find an array element with a specific name and change +the iActValue data member of that element:

+... +_LIT(KFindName,"A.Bloggs"); +bankact.iActName = KFindName; +... +TInt position; +if (anArray->FindIsq(bankact,actNameKey,position)) + { + // array element NOT found + ... + } +else + { + (*anArray)[position].iActValue = 40,000,000; + ... + }

Notes

Sorting a packed array +is achieved using the SortL() member function.
Although the example +uses an array of fixed length objects and a TKeyArrayFix object, +the same techniques apply to variable length and packed arrays.