I am new in iPhone programming. Can anyone tell how parse the JSON string in iPhone? 
I'm using JSON parsing in my application. This is my JSON data:
The JSON format is dz.

```
{  
"firstName": "John",  
"lastName": "Smith",  
"age": 25,  
 "address": {  
              "streetAddress": "21 2nd Street",  
          "city": "New York",  
          "state": "NY",  
         "postalCode": "10021"  
         }
}  

```

How can I do this parsing?