如何将NSData保存到数据库

Question

I have a object of UILabel

UILabel *label1 = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 200, 200)];
label1.text = @"LABEL AREA";

I want to save it in my databse(sqlite).

My idea is to convert this object to a NSData using

[NSKeyedArchiver archivedDataWithRootObject:label1];               //step1

and convert this NSData to a NSString(step2), then save that NSString to the database(step3).

When I need my UILabel. I can get the NSString from database, convert it to NSData, and use

[NSKeyedUnarchiver unarchiveObjectWithData:];

to get my UILabel.

But I have a problem in "step 2". When I use

NSString *strWithEncode = [[NSString alloc] initWithData:dataRaw encoding:NSUTF8StringEncoding];

I get a null object. I don't know the reason. Why?

Thanks a lot!

Answer 1

You could either a) Store the data as a BLOB or b) Store the text of the string instead of the actual string. B seems like a better choice because you will be storing less data, and the contents of the DB will be human readable, should you need that information for debugging later on.

Answer 2

Because the NSData represents an encoded UILabel and not a UTF-8 encoded NSString, trying to initialize a UTF-8 string from the data will almost certainly not work. If you absolutely have to store the data as a string, try using some form of data-to-string encoding. Try using base32 or base64.