'NSInvalidArgumentException', reason: '-[__NSCFString allKeys]: unrecognized selector sent to instance 0x7ae2f750' - ios

Question

responce stored in dictionary :
dict_Profile=[response objectForKey:#"unknown_object"];
after that am doing like this
lbl_HeadName.text=[NSString stringWithFormat:#"%#",[dict_Profile objectForKey:#"FirstName"]];
this data getting from server
getUserProfileResponse
{
"status_code" = 200;
"unknown_object" = "{
ID:90,FirstName:Dr.Alekhya,LastName:Kasoju,GivenName:Alekhya Kumar,DOB:1993-07-15T00:00:00,_DcotorAction:edit,
Languages:[44,45,46],
Designations[5102],PersonalEmailID:alekhya.k#inativetech.com,
PersonalContactNo:7675879511,Medical_Council_ID:MED003,
ProfilePhoto:Doctor_9015763545-Attractive-young-Indian-Female-Doctor-with-notepad-isolated-on-white--Stock-Photo.jpg,PracticeStartedOn:2013,LanguagesList:[{Key:44,Value:Telugu},{Key:45,Value:English},{Key:46,Value:Hindi},{Key:47,Value:Tamil},{Key:138,Value:Urdhu},{Key:139,Value:oriya},{Key:140,Value:Bengali},{Key:141,Value:kanada},{Key:142,Value:Marati},{Key:144,Value:Kashmiri},{Key:198,Value:card},{Key:4304,Value:malayalam},{Key:4310,Value:Sanksrit},{Key:4311,Value:German},{Key:4350,Value:Japanies},{Key:5275,Value:PGDMC},{Key:5518,Value:physicians}],DesignationsList:[{Key:5100,Value:Allergist or Immunologist},{Key:5101,Value:Anesthesiologist },{Key:5102,Value:Cardiologist},{Key:5103,Value:Dermatologist },{Key:5104,Value:Gastroenterologist},{Key:5105,Value:Hematologist/Oncologist },{Key:5106,Value:Internal Medicine Physician },{Key:5108,Value:Nephrologist\U00c2\U00a0 },{Key:5109,Value:Neurologist\U00c2\U00a0 },{Key:5110,Value:Neurosurgeon },{Key:5111,Value:Obstetrician },{Key:5112,Value:Gynecologist},{Key:5113,Value:Nurse-Midwifery },{Key:5114,Value:Occupational Medicine Physician},{Key:5115,Value:Ophthalmologist },{Key:5116,Value:Oral and Maxillofacial Surgeon\U00c2\U00a0 },{Key:5117,Value:Orthopaedic Surgeon },{Key:5118,Value:Otolaryngologist\U00c2\U00a0(Head and Neck Surgeon)\U00c2\U00a0 },{Key:5119,Value:Pathologist\U00c2\U00a0 },{Key:5120,Value:Pediatrician },{Key:5121,Value:Plastic Surgeon\U00c2\U00a0 },{Key:5122,Value:Podiatrist\U00c2\U00a0 },{Key:5123,Value:Psychiatrist },{Key:5124,Value:Pulmonary Medicine Physician },{Key:5125,Value:Radiation Onconlogist\U00c2\U00a0 },{Key:5126,Value:Diagnostic Radiologist },{Key:5127,Value:Rheumatologist\U00c2\U00a0 },{Key:5128,Value:Urologist },{Key:5129,Value:Orthopedist},{Key:5216,Value:Ayurveda},{Key:5519,Value:physicians},{Key:5897,Value:Ayurved},{Key:5898,Value:Ayurvedic},{Key:7442,Value:Homeopathy Doctor},{Key:7921,Value:Homeopath},{Key:8770,Value:Gynecologist/Obstetrician},{Key:8771,Value:MBBS,DGO},{Key:8774,Value:Spine Surgeon},{Key:8775,Value:MS (Ortho), FNB - Spine Surgery},{Key:8779,Value:Gastroentrology Surgeon},{Key:8780,Value:General Surgeon},{Key:8781,Value:Dentist},{Key:8783,Value:ENT},{Key:8784,Value:Radiology},{Key:8785,Value:General Surgery},{Key:8786,Value:Homeopathic},{Key:8787,Value:Trichologist},{Key:8788,Value:Diabetologist},{Key:8791,Value:Laboratory Medicine},{Key:8801,Value:Hematologist}],YearsList:[{Key:0,Value:-- Select Year--},{Key:2016,Value:2016},{Key:2015,Value:2015},{Key:2014,Value:2014},{Key:2013,Value:2013},{Key:2012,Value:2012},{Key:2011,Value:2011},{Key:2010,Value:2010},{Key:2009,Value:2009},{Key:2008,Value:2008},{Key:2007,Value:2007},{Key:2006,Value:2006},{Key:2005,Value:2005},{Key:2004,Value:2004},{Key:2003,Value:2003},{Key:2002,Value:2002},{Key:2001,Value:2001},{Key:2000,Value:2000},{Key:1999,Value:1999},{Key:1998,Value:1998},{Key:1997,Value:1997},{Key:1996,Value:1996},{Key:1995,Value:1995},{Key:1994,Value:1994},{Key:1993,Value:1993},{Key:1992,Value:1992},{Key:1991,Value:1991},{Key:1990,Value:1990},{Key:1989,Value:1989},{Key:1988,Value:1988},{Key:1987,Value:1987},{Key:1986,Value:1986},{Key:1985,Value:1985},{Key:1984,Value:1984},{Key:1983,Value:1983},{Key:1982,Value:1982},{Key:1981,Value:1981},{Key:1980,Value:1980},{Key:1979,Value:1979},{Key:1978,Value:1978},{Key:1977,Value:1977},{Key:1976,Value:1976},{Key:1975,Value:1975},{Key:1974,Value:1974},{Key:1973,Value:1973},{Key:1972,Value:1972},{Key:1971,Value:1971},{Key:1970,Value:1970},{Key:1969,Value:1969},{Key:1968,Value:1968},{Key:1967,Value:1967},{Key:1966,Value:1966},{Key:1965,Value:1965},{Key:1964,Value:1964},{Key:1963,Value:1963},{Key:1962,Value:1962},{Key:1961,Value:1961},{Key:1960,Value:1960},{Key:1959,Value:1959},{Key:1958,Value:1958},{Key:1957,Value:1957},{Key:1956,Value:1956},{Key:1955,Value:1955},{Key:1954,Value:1954},{Key:1953,Value:1953},{Key:1952,Value:1952},{Key:1951,Value:1951},{Key:1950,Value:1950},{Key:1949,Value:1949},{Key:1948,Value:1948},{Key:1947,Value:1947},{Key:1946,Value:1946},{Key:1945,Value:1945},{Key:1944,Value:1944},{Key:1943,Value:1943},{Key:1942,Value:1942},{Key:1941,Value:1941},{Key:1940,Value:1940},{Key:1939,Value:1939},{Key:1938,Value:1938},{Key:1937,Value:1937},{Key:1936,Value:1936},{Key:1935,Value:1935},{Key:1934,Value:1934},{Key:1933,Value:1933},{Key:1932,Value:1932},{Key:1931,Value:1931},{Key:1930,Value:1930},{Key:1929,Value:1929},{Key:1928,Value:1928},{Key:1927,Value:1927},{Key:1926,Value:1926},{Key:1925,Value:1925},{Key:1924,Value:1924},{Key:1923,Value:1923},{Key:1922,Value:1922},{Key:1921,Value:1921},{Key:1920,Value:1920},{Key:1919,Value:1919},{Key:1918,Value:1918},{Key:1917,Value:1917},{Key:1916,Value:1916}]}";
}

Answer 1

as you see, the unknown_object in your response is just a string, not a json object,so it will be translated to a NSString * object, but not a dictionary.
if you want unknown_object to be a dictionary, you can adjust your response like following:
getUserProfileResponse
{
"status_code" = 200;
"unknown_object" = {
"ID" : 90,
"FirstName" : "Dr.Alekhya",
......
}
}
or
make your unknown_object to a valid json string,then transfer it back to a dictionary, like this:
NSData *data = [#"{\"id\" : 1}" dataUsingEncoding:NSUTF8StringEncoding];
[NSJSONSerialization JSONObjectWithData:data
options:NSJSONWritingPrettyPrinted
error:nil];

Answer 2

allKeys is a property of Dictionary to which provides array of Keys in that dictionary.
Looks like you are calling allKeys on NSString object, Because of that you are getting this error.
Convert your String object to valid Dictionary. Try below
NSString *jsonString = "your string"
NSData *data = [jsonString dataUsingEncoding:NSUTF8StringEncoding];
id json = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
Hope it helps.

Answer 3

The response that you are getting is not actually a dictionary, so you need to convert NSSting to NSDictionary.
NSString *response = #"{ \"status_code\" : 200, \"unknown_object\" : { \"ID\" : \"90\", \"FirstName\" : \"Dr.Alekhya\"} }";
NSError *error;
NSData *data = [response dataUsingEncoding:NSUTF8StringEncoding];
NSDictionary *dict_Profile = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:&error];
NSLog(#"res = %#", dict_Profile);
//get data from dictionary
NSString *strName = [NSString stringWithFormat:#"%#",[[dict_Profile objectForKey:#"unknown_object"] valueForKey:#"FirstName"]];
NSLog(#"FirstName = %#", strName);

Answer 4

it may help you:
NSDictionary *jsonDic = [NSJSONSerialization JSONObjectWithData:[response dataUsingEncoding:NSUTF8StringEncoding] options:NSJSONReadingAllowFragments error:nil];