iphone - SQLite 查询中的 NSInteger 变量

Question

任何人都可以帮助我在 iOS 应用程序中进行 SQLite 查询吗？我想进行查询，这将取决于 WHERE 子句中的 NSInteger 变量，但我不知道如何将变量添加到查询中。

我试过这样的:

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

但这当然行不通。

谢谢。

编辑

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  

Answer 1

如果我理解正确的话，您想将一个整数变量注入(inject)到 SQL 查询中。如果是这样，类似下面的内容应该可以完成这项工作:

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

%d 是整数的修饰符。假设 makeSQL 选择器接受 NSString SQL 字符串