How to filter the input box by entering only letters and numbers

How to filter the input box by entering only letters and numbers 1.

Uitextfielddelegate protocol.

2. Define the following variables in the header file:

// Restrict the user to only letters and numbers

# Define kalphanum @ "abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz0123456789"

3. In the implementation file:

Set the delegate of the textfiled object to self:

M_accountfield = [[uitextfield
Alloc] initwithframe: cgrectmake (89,
26,243,
33)];

M_accountfield.borderstyle =
Uitextborderstylenone;

M_accountfield.font = fieldfont;

M_accountfield.delegate =
Self;

// Uitextfielddelegate-(bool) textfieldshouldreturn :( uitextfield *) textfield; {// user end input [textfield resignfirstresponder]; return yes;}-(bool) textfield :( uitextfield *) textfield shouldchangecharactersinrange :( nsange) range replacementstring :( nsstring *) string // return no to not change text {nscharacterset * cs; cs = [[nscharacterset limit: kalphanum] invertedset]; nsstring * filtered = [String componentsseparatedbycharactersinset: CS] componentsjoinedbystring: @ ""]; bool basic = [String isequaltostring: Filtered]; return basic ;}