NSInteger Variable at SQLite Query

Question

Can anyone help me with SQLite query in my iOS app? I want to make query, which will depend on NSInteger varialbe at WHERE clause, but i dont know how to add variable into query.

I tried something like this:

MySqlite *sqlConnect = [[MySqlite alloc] init];  
sqlite3_stmt *statement = [sqlConnect makeSQL:"select * from table where id = %i", myIntegerVariable - 1];

But of course it doesn't work.

Thanks.

EDIT

MySqlite.h

#import <Foundation/Foundation.h>  
#import <sqlite3.h>  

@interface MySqlite : NSObject {  

}  
- (sqlite3_stmt *)makeSQL:(char *)sql;  

@end

MySqlite.m

#import "MySqlite.h"  

@implementation MySqlite  

NSString *dbFileName = @"data.sqlite";  

- (void)createEditableCopyOfDatabaseIfNeeded {  

NSFileManager *fileManager = [NSFileManager defaultManager];  
NSError *error;  

NSString *writableDBPath = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0]  
                            stringByAppendingPathComponent:dbFileName];  

if ([fileManager fileExistsAtPath:writableDBPath]){  
    return;  
}  

NSString *defaultDBPath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:dbFileName];  

if (! [fileManager copyItemAtPath:defaultDBPath toPath:writableDBPath error:&error] ) {  
    NSLog(@"Fail edit db");  
}  
}  

- (sqlite3 *) getDBConnection{  

[self createEditableCopyOfDatabaseIfNeeded];  

sqlite3 *DBConnection;  

NSString *path = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0]   
                  stringByAppendingPathComponent:dbFileName];  

if( sqlite3_open([path UTF8String], &DBConnection) != SQLITE_OK) {  
    NSLog(@"Fail open db");  
    return FALSE;  
}  

return DBConnection;  
}  

- (sqlite3_stmt *)makeSQL:(char *)sql{  
NSLog(@"Executing query: %s", sql);  

sqlite3_stmt *statement = nil;  

sqlite3 *db = [self getDBConnection];  

if ( db ) {  
    if (sqlite3_prepare_v2(db, sql, -1, &statement, NULL) != SQLITE_OK) {  
        NSLog(@"Error at query: %s", sqlite3_errmsg(db));  
    }  
}  
else {  
    NSLog(@"Error connect to db");  
}  

return statement;  
}  


@end

Tried to put it into [NSString stringWithFormat:@"select * from table where id = %i", myIntegerVariable - 1]? — ott--
– ott--, Commented Sep 30, 2011 at 15:25
It is my class for connecting to the database and making queries. — Tom
– Tom, Commented Sep 30, 2011 at 15:28

Suhail Patel · Accepted Answer · 2011-09-30 15:41:05Z

1

If I understood you correctly, you want to inject an integer variable into the SQL Query. If so, something like below should do the job:

MySqlite *sqlConnect = [[MySqlite alloc] init];  
sqlite3_stmt *statement = [sqlConnect makeSQL:[[NSString stringWithFormat:@"select * from table where id = %d", myIntegerVariable - 1] UTF8String]];

%d is the modifier for an Integer. That is assuming that the makeSQL selector takes in an NSString SQL String

edited Sep 30, 2011 at 15:41

answered Sep 30, 2011 at 15:31

Suhail Patel

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4 Comments

Tom Over a year ago

It doesn't work. Make sql expect (char *). This is the method: -(sqlite3_stmt *)makeSQL:(char *)sql.

Suhail Patel Over a year ago

I have modified my code sample above, the UTF8String addition will give you a char string

Tom Over a year ago

Show me this: Passing argument 1 of 'makeSQL:' discards qualifiers from pointer target type. Semantic Issue: Sending 'const char *' to parameter of type 'char *' discards qualifiers

Tom Over a year ago

I have changed my -(sqlite3_stmt *)makeSQL:(char *)sql method to -(sqlite3_stmt *)makeSQL:(const char *)sql and it works fine. Thank you!

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