extjs - Sencha touch selectfield Placeholder -

How can I add a selectfield placeholder to the sencha touch ..

Here's my code

here placeholder is not visible I can only see the first text value option in the list.

  {text: 'Select a client', value: 'select'}, as   
 The first option but, in this case I am unable to validate it by verifying my model .. No one plaz helps me solve this problem..Your help is highly appreciated .. Thanks in advance  
 
  
 
  auto select  for property  false  Remove quote marks from (and all Julian Configuration Option):  
  {xtype: 'selectfield', label: 'subclient', itemId: 'subclient', name: 'subclient', labelWrap: correct, auto select: incorrect , Location: Holder: Select ', {Text:' standard sale '}, {text:' short sale ', value:' Bank of America '}, {text:' REO ', value:' RO '}]   
},