SQLite结果集包含空值

Question

I get a result set from sqlite which looks something like this:

Null, 23, 34, 45 (being (say) 4 items returned)

The null value is correct - however when I try to add it to an array in objective-c with the following code I get an error - Null cstring - here's my code:

[array addObject:[NSString stringWithUTF8String:(char *)sqlite3_column_text(statement, 0)]];

I tried unsuccessfully testing for the null before adding it to the array and replacing it with a zero but so far no luck.

Could someone please help me to handle the null value so I can add maybe a zero into the array.

Thanks for any help.

Answer 1

As Hot Licks said, check the return value and either add a string created from that, or add [NSNull null] .

const unsigned char *column0 = sqlite3_column_text(statement, 0);
if (column0)
    [array addObject:[NSString stringWithUTF8String:(const char *)column0]];
else
    [array addObject:[NSNull null]];

Answer 2

Handling null as suggested is a good option.

You can also modify queries to force column to always be TEXT using CAST(column_name AS TEXT) , or force NULLs to empty strings using COALESCE(column_name, '') .