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<concept id="GUID-059326DB-E7A4-5CB8-BCA7-FF0C71D9D1C7" xml:lang="en"><title>How

to access elements</title><shortdesc>The elements of an array can be accessed by specifying the position

of the element in the array.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>The elements of an array can be referenced using the indexing  <codeph>operator[]</codeph> and

specifying the position of the element.</p>

<p>For all arrays <i>except</i> the <codeph>RArray&lt;class T&gt;</codeph> and <codeph>RPointerArray&lt;class T&gt;</codeph> types,

the <codeph>At()</codeph> member function can also be used.</p>

<p>All of the following code fragments use a <codeph>CArrayFixFlat&lt;class T&gt;</codeph> array.</p>

<p>This code constructs a fixed flat array containing the required number

of <codeph>TInt</codeph> type elements - in this case four.</p>

<p>The indexing operator is used to fetch the value of the second element.

This element is then changed, showing two different methods for changing the

element: the <codeph>At()</codeph> function and the <codeph>[]</codeph> operator.</p>

<codeblock id="GUID-44519EEA-85BA-54CF-9F4A-E67B043C8837" xml:space="preserve">CArrayFixFlat&lt;TInt&gt;* array;

array = new CArrayFixFlat<TInt>(4);

...

for (TInt value = 0; value < 4; value++)

 array->AppendL(value);

...

TInt somevalue = (*array)[1];  //fetch the element

TInt somevalue = array->At(1);  //... alternative way

(*array)[1]    = 21;    //change the element

array-&gt;At(1)   = 21;    // ... alternative way</codeblock>

<section id="GUID-DD4808A9-0989-4A2E-B83C-B735BEDE0677"><title>Accessing functions</title> <p>If the array elements are objects

of a class with member functions, these functions can be easily accessed as

shown in the following code fragment:</p> <codeblock id="GUID-DD0C968E-B164-5EAA-9188-F0A323197652" xml:space="preserve">class TMyClass

 {

public :

 void SetValue(TInt aval);

 TInt GetValue();

private

 TUint iValue;

 };</codeblock> <codeblock id="GUID-39DDFF64-B1FC-5D93-8552-9D0FF4E5B6BD" xml:space="preserve">CArrayFixFlat&lt;TMyClass&gt;* array;          // an array of

                                         // TMyClass objects

TMyClass myclass;

array = new CArrayFixFlat<TMyClass>(1);

array->AppendL(myclass);

(*array)[0].SetValue(21);</codeblock> </section>

<section id="GUID-B2AE92D8-239C-4711-AA85-EEE9D333288C"><title>Accessing functions of CBase derived objects</title> <p>Where

the elements are pointers to <codeph>CBase</codeph> derived objects (i.e.

elements of an array of type <codeph>CArrayPtrFlat</codeph> or <codeph>CArrayPtrSeg</codeph>),

the members of those <codeph>CBase</codeph> derived objects can easily be

accessed. For example, an array of pointers to <codeph>CElement</codeph> objects

can be accessed as follows:</p> <codeblock id="GUID-D35D517A-0DB1-59A8-A6A3-BFDDF1C4610B" xml:space="preserve">CArrayPtrFlat&lt;CElement&gt;* ptrflat;

...

ptrflat = new (ELeave) CArrayPtrFlat<CElement>(16)

...

...   // add elements to ptrflat

...

(*ptrflat)[0]->SetTextL(_LIT("New text for the first CElement"));

ptrflat-&gt;At(1)-&gt;SetTextL(_LIT("New text for the second CElement"));</codeblock> <p>(where <codeph>SetTextL()</codeph> is

a member function of <codeph>Celement)</codeph>.</p> <p>Note that both <codeph>At()</codeph> and

the index <codeph>operator[]</codeph> return a reference to the object in

the array. </p> </section>

<section id="GUID-C8FB1FAE-F331-4B1D-9FEA-982A14986E42"><title>Refreshing the pointer</title> <p>If a pointer to the referenced

object is taken, be aware that the pointer value may become invalid once elements

are added to, or removed from the array. In this event, always refresh the

pointer. </p> <codeblock id="GUID-FE89CB4A-821E-515D-B963-58D4C288E385" xml:space="preserve">class TMyClass

 {

public :

 void SetValue(TInt aval);

 TInt GetValue();

private

 TUint iValue;

 };</codeblock> <codeblock id="GUID-D727EFF4-DA87-54F8-8E4C-761F11E5726A" xml:space="preserve">CArrayFixFlat&lt;TMyClass&gt;* array;

...

TMyClass myclass;

array = new CArrayFixFlat<TMyClass>(16);

...

for (TInt val = 0; val < 10; val++)

 {

 myclass.SetValue(val)

 array->AppendL(myclass;

 }

...

TMyClass* myptr;

myptr = &(array->At(9));

myptr->GetValue();  // references the tenth element

array->Delete(0,4); // Delete first four elements

array->Compress();  

myptr->GetValue();  // myptr is invalid. An exception may occur

...</codeblock> <p>After deleting the first four elements, <codeph>myptr</codeph> points

to a location outside the logical array. Once the array has been compressed,

the pointer is invalid. </p> </section>