Sqlite helper function for Objective C

SqliteHelper

#import "SqliteHelper.h"

@implementation SqliteHelper

static SqliteHelper *helper;

+(SqliteHelper*) get;{
    if(helper==nil){
        helper=[[SqliteHelper alloc] init];
    }
    return helper;
}

-(id) init;{
    NSString *docDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) firstObject];
    
    NSString *sqLiteDb = [NSString stringWithFormat:@"%@/%@", docDirectory, SQLLITEDB];
    if (sqlite3_open([sqLiteDb UTF8String], &database) != SQLITE_OK) {
        NSLog(@"Failed to open database!");
    }else{
        NSString *initQuery = [NSString stringWithFormat:@"CREATE TABLE IF NOT EXISTS %@ (key TEXT PRIMARY KEY,value TEXT);", SQLLITE_TABLE];
        sqlite3_stmt *statement;
        if(sqlite3_prepare_v2(database, [initQuery UTF8String], -1, &statement, nil) \
           ==SQLITE_OK) {
            sqlite3_step(statement);
        }
    }
    return self;
}



-(NSString *)getData: (NSString*) key {
    NSString *data = nil;
    NSString *query = [NSString stringWithFormat:@"SELECT value from %@ where key \
                       = '%@'", SQLLITE_TABLE,key];

    sqlite3_stmt *statement;
    if (sqlite3_prepare_v2(database, [query UTF8String], -1, &statement, nil)\
        == SQLITE_OK) {
        while (sqlite3_step(statement) == SQLITE_ROW) {
            char *dataChars = (char *) sqlite3_column_text(statement, 0);
            data = [[NSString alloc] initWithUTF8String:dataChars];
        }
        sqlite3_finalize(statement);
    }
    return data;
}


-(Boolean) setItem:(NSString*) key value:(NSString*) value;
{
    Boolean flag = false;
    @try {
        NSString *query = [NSString stringWithFormat:@"replace into %@ (key,value)values('%@','%@')",\
                           SQLLITE_TABLE, key, value];
        sqlite3_stmt *statement;
        if (sqlite3_prepare_v2(database, [query UTF8String], -1, &statement, nil)\
            == SQLITE_OK) {
            sqlite3_step(statement);
            flag = true;
        }else{
            flag = false;
        }
    } @catch (NSException *e) {
        ENInfo(@"%@", [e description]);
        flag = false;
    }
    return flag;
}


-(Boolean) removeItem:(NSString*) key;
{
    Boolean flag = false;
    @try {
        NSString *query = [NSString stringWithFormat:@"delete from %@ where key='%@'", \
                         SQLLITE_TABLE, key];
        sqlite3_stmt *statement;
        if (sqlite3_prepare_v2(database, [query UTF8String], -1, &statement, nil)\
            == SQLITE_OK) {
            sqlite3_step(statement);
            flag = true;
        }else{
            flag = false;
        }
    } @catch (NSException *e) {
        ENDebug(@"%@", [e description]);
        flag = false;
    }
    return flag;
}

- (void)dealloc
{
    sqlite3_close(database);
}

@end