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 TBankAct class is defined as:

-class TBankAct - { -public : - TBuf<32> iActName; - TUint iActNum; - TUint iActValue; - } -

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

-CArrayFixFlat<TBankAct> *anArray; -anArray = new CArrayFixFlat<TBankAct>(3); -TBankAct bankact; -... -_LIT(KName1,"A.Bloggs"); -_LIT(KName2,"F.B.Wittering"); -_LIT(KName3,"Z.Makepeace"); -... -bankact.iActName = KName1; -bankact.iActNum = 3; -bankact.iActValue = 300; -anArray->AppendL(bankact); -... -bankact.iActName = KName2; -bankact.iActNum = 1; -bankact.iActValue = 6000; -anArray->AppendL(bankact); -... -bankact.iActName = KName3; -bankact.iActNum = 2; -bankact.iActValue = 32; -anArray->AppendL(bankact); -... -

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.

+ + + + + +How +to use array keysThis document describes 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 TBankAct class is defined as:

+class TBankAct + { +public : + TBuf<32> iActName; + TUint iActNum; + TUint iActValue; + } +

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

+CArrayFixFlat<TBankAct> *anArray; +anArray = new CArrayFixFlat<TBankAct>(3); +TBankAct bankact; +... +_LIT(KName1,"A.Bloggs"); +_LIT(KName2,"F.B.Wittering"); +_LIT(KName3,"Z.Makepeace"); +... +bankact.iActName = KName1; +bankact.iActNum = 3; +bankact.iActValue = 300; +anArray->AppendL(bankact); +... +bankact.iActName = KName2; +bankact.iActNum = 1; +bankact.iActValue = 6000; +anArray->AppendL(bankact); +... +bankact.iActName = KName3; +bankact.iActNum = 2; +bankact.iActValue = 32; +anArray->AppendL(bankact); +... +

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); +...