sqlite3 insert and read BLOB data in database

Question

I need to read and write BLOB data to a database. Here is my structure table

    #define CREATE_TABLE_USERS_SQL \"CREATE TABLE IF NOT EXISTS %@ ( \\
UserID I         


        

Answer 1

This code fails:

   NSData * buf2 = [[NSData alloc] init];
   sqlite3_column_blob(statement, 5);
   buf2 = sqlite3_column_bytes(statement, 5);
   user.image = [UIImage imageWithData: buf2];

You are calling the SQLite functions in the correct order. According to the SQLite docs:

The safest and easiest to remember policy is to invoke these routines in one of the following ways:

• sqlite3_column_text() followed by sqlite3_column_bytes()
• sqlite3_column_blob() followed by sqlite3_column_bytes()
• sqlite3_column_text16() followed by sqlite3_column_bytes16()

In other words, you should call sqlite3_column_text(), sqlite3_column_blob(), or sqlite3_column_text16() first to force the result into the desired format, then invoke sqlite3_column_bytes() or sqlite3_column_bytes16() to find the size of the result. Do not mix calls to sqlite3_column_text() or sqlite3_column_blob() with calls to sqlite3_column_bytes16(), and do not mix calls to sqlite3_column_text16() with calls to sqlite3_column_bytes().

However, buff2 is an integer, not a data pointer. sqlite3_column_bytes tells you how many bytes are in the blob.