CODEWITHSUNDEEP
iphonesqlitenullnsdata
Pradhyuman sinh
Pradhyuman sinh

Reputation: 3928

NSData return Null issue

In my application I stored multiple images in my database.
Where my database field type is blob.

Storing the image data works well but when i get image data from database using below code 

   NSData *photodata=[[NSData alloc] initWithBytes:sqlite3_column_blob(compiledStmt, 12) length:sqlite3_column_bytes(compiledStmt, 12)];

But the field contains null data it returns me <3c3e> in place of null value.
And I inserted data using below query 

   strQuery_DB = [NSString stringWithFormat:@"update tbl_project_review set answer ='%@',comment ='%@',photodata='%@' where prjid=%d",temp,escapedStr1,tempdata,prjid];

Upvotes: 2

Views: 219

Answers (3)

dreamlax
dreamlax

Reputation: 95325

When you use the %@ specifier with the stringWithFormat: method, it invokes the description method of the respective argument. For NSData objects, this returns a hexadecimal representation of the data surrounded by < and >. For an empty NSData object it will return the string <> and this is what is being inserted into the database. This is probably not what you want to do, since this will also double the size of your image data unnecessarily.

You should use parameterised query functions such as sqlite_bind_blob. This will make it easier to deal with data input. Basically, you need to change your update query to something like the following (add appropriate error checking, etc):

const char sql[] = "update tbl_project_review set answer = ?, comment = ?, photodata = ? where prjid = ?";
sqlite3_stmt *stmt = NULL;
sqlite3_prepare_v2(db, sql, sizeof sql, &stmt, NULL);

sqlite3_bind_text(stmt, 1, [tmp UTF8String], -1, SQLITE_TRANSIENT);
sqlite3_bind_text(stmt, 2, [escapedStr1 UTF8String], -1, SQLITE_TRANSIENT);
sqlite3_bind_blob(stmt, 3, [tempdata bytes], [tempdata length], SQLITE_TRANSIENT);
sqlite3_bind_int(stmt, 4, prjid);

sqlite3_step(stmt); // check for SQLITE_DONE

Upvotes: 2

Paras Joshi
Paras Joshi

Reputation: 20541

bellow is simple code for retrive image from database try..

                NSString *imgurl=[NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 3)];
                int length = sqlite3_column_bytes(compiledStatement, 4);
//                NSData *data       = [NSData dataWithBytes:sqlite3_column_blob(compiledStatement, 4) length:length];
                NSString *imageString=[NSString stringWithCharacters:sqlite3_column_blob(compiledStatement, 4) length:length];
                UIImage *personImage=[UIImage imageNamed:imageString];

i hope this help you...

Upvotes: 0

Narayana Rao Routhu
Narayana Rao Routhu

Reputation: 6323

Storing image as blob in DB is bad procedure. you need to save image in your cache directory and then you need to save path of image in DB is good.

Upvotes: 2

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