从sqLite数据库ios iphone应用程序中检索数据

Question

我正在构建一个数据库，我想从保存在数据库中的对象中检索特定数据。

这是我的代码：

//databaseMainViewController.m
//Create and database and save data

@implementation databaseMainViewController

@synthesize customer, code1,code2;


-(void) createTable: (NSString*)tableName
         withField1: (NSString*)field1
         withField2: (NSString*)field2
         withField3: (NSString*)field3
         withField4: (NSString*)field4; {

    char*err;
    NSString*sql = [NSString stringWithFormat:@"CREATE TABLE IF NOT EXISTS '%@' ('%@'"
                                              "TEXT PRIMARY KEY, '%@'TEXT, '%@'TEXT, '%@'TEXT);", tableName, field1, field2, field3, field4];

    if(sqlite3_exec(db, [sql UTF8String], NULL, NULL, &err)!=SQLITE_OK){

        sqlite3_close(db);
        NSAssert(0, @"DCould not create table");

    }

    else {
        NSLog(@"table created");
    }
}

//file path to database
-(NSString*)filePath {
    NSArray*paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    return [[paths objectAtIndex:0]stringByAppendingPathComponent:@"bp.sql"];
}

//open database
-(void)openDB {

    if(sqlite3_open([[self filePath]UTF8String], &db) !=SQLITE_OK) {
        sqlite3_close(db);
        NSAssert(0, @"Databese failed to open");
    }

        else {
            NSLog(@"database opemed");
        }


}

- (IBAction)save:(id)sender {

    NSString*customers = customer.text;
    NSString*codeOne = code1.text;
    NSString*codeTwo = code2.text;
    NSDate*theDate = [NSDate date];

    NSString*sql= [NSString stringWithFormat:@"INSERT INTO summary ('theDate','customer','code1','code2')VALUES ('%@','%@','%@','%@')", theDate, customers,codeOne, codeTwo];

    char*err;

    if(sqlite3_exec(db, [sql UTF8String], NULL, NULL, &err)!=SQLITE_OK){

        sqlite3_close(db);
        NSAssert(0, @"Could not update table");

    }

    else {
        NSLog(@"table updated");
    }

    customer.text = @"";
    code1.text = @"";
    code2.text = @"";



}

- (void)viewDidLoad
{
    [self openDB];
    [self createTable:@"summary" withField1:@"theDate" withField2:@"customer" withField3:@"code1" withField4:@"code2"];
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

然后我有代码来检索数据并将它们放在主列表中

#import "databaseFlipsideViewController.h"
#import "detailViewController.h"


@interface databaseFlipsideViewController ()

@end

@implementation databaseFlipsideViewController

@synthesize entries;

//file path to database
-(NSString*)filePath {
    NSArray*paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    return [[paths objectAtIndex:0]stringByAppendingPathComponent:@"bp.sql"];
}

//open database
-(void)openDB {

    if(sqlite3_open([[self filePath]UTF8String], &db) !=SQLITE_OK) {
        sqlite3_close(db);
        NSAssert(0, @"Databese failed to open");
    }

    else {
        NSLog(@"database opemed");
    }


}

- (void)viewDidLoad
{
    entries = [[NSMutableArray alloc]init];
    [self openDB];
    NSString*sql = [NSString stringWithFormat:@"SELECT * FROM summary"];
    sqlite3_stmt*statement;

    if (sqlite3_prepare_v2(db, [sql UTF8String], -1, &statement, nil)==SQLITE_OK) {

        while (sqlite3_step(statement)==SQLITE_ROW) {
            char*field1 = (char*)sqlite3_column_text(statement, 0);
            NSString*field1Str = [[NSString alloc]initWithUTF8String:field1];

            char*field2 = (char*)sqlite3_column_text(statement, 1);
            NSString*field2Str = [[NSString alloc]initWithUTF8String:field2];

            char*field3 = (char*)sqlite3_column_text(statement, 2);
            NSString*field3Str = [[NSString alloc]initWithUTF8String:field3];

            char*field4 = (char*)sqlite3_column_text(statement, 3);
            NSString*field4Str = [[NSString alloc]initWithUTF8String:field4];

            NSString*str = [[NSString alloc]initWithFormat:@"%@", field2Str ];
            [entries addObject:str];
        }
    }

    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

#pragma mark - Actions

- (IBAction)done:(id)sender
{
    [self.delegate flipsideViewControllerDidFinish:self];
}

-(NSInteger)numberOfSectionsInTableView:(UITableView*)tableView {

    //Return the number of sections
    return 1;
}

-(NSString*)tableView:(UITableView*)tableView titleForHeaderInSection:(NSInteger)section {
    NSString*myTitle = [[NSString alloc]initWithFormat:@"History"];
    return myTitle;
}

-(NSInteger)tableView:(UITableView*)tableView numberOfRowsInSection:(NSInteger)section{

    return [entries count];
    NSLog(@"%d",[entries count]);


}

-(UITableViewCell*)tableView:(UITableView*)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    NSLog(@"test");

    static NSString*cellIdentifier = @"Cell";
    UITableViewCell*cell = [tableView dequeueReusableCellWithIdentifier:cellIdentifier forIndexPath:indexPath];

    cell.textLabel.text = [self.entries objectAtIndex:indexPath.row];
    return cell;

}

在此之后我遇到了问题，因为当我点击列表中的一个名称时，应用程序会转到另一个视图，其中包含有关名称的详细信息。但每个名字的细节都是一样的。

这是detailViewController的代码：

#import "detailViewController.h"

@interface detailViewController ()

@end

@implementation detailViewController

@synthesize customerLabel,code1Label,code2Label,dateLabel;

//file path to database
-(NSString*)filePath {
    NSArray*paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    return [[paths objectAtIndex:0]stringByAppendingPathComponent:@"bp.sql"];
}

//open database
-(void)openDB {

    if(sqlite3_open([[self filePath]UTF8String], &db) !=SQLITE_OK) {
        sqlite3_close(db);
        NSAssert(0, @"Databese failed to open");
    }

    else {
        NSLog(@"database opemed");
    }


}

- (IBAction)back:(id)sender
{
    [self.delegate detailViewControllerDidFinish:self];
}

- (void)viewDidLoad
{
    [self openDB];
    NSString*sql = [NSString stringWithFormat:@"SELECT * FROM summary"];
    sqlite3_stmt*statement;


    if (sqlite3_prepare_v2(db, [sql UTF8String], -1, &statement, nil)==SQLITE_OK) {

        while (sqlite3_step(statement)==SQLITE_ROW) {


            char*field1 = (char*)sqlite3_column_text(statement, 0);
            NSString*field1Str = [[NSString alloc]initWithUTF8String:field1];

            char*field2 = (char*)sqlite3_column_text(statement, 1);
            NSString*field2Str = [[NSString alloc]initWithUTF8String:field2];

            char*field3 = (char*)sqlite3_column_text(statement, 2);
            NSString*field3Str = [[NSString alloc]initWithUTF8String:field3];

            char*field4 = (char*)sqlite3_column_text(statement, 3);
            NSString*field4Str = [[NSString alloc]initWithUTF8String:field4];



            customerLabel.text = field2Str;
            code1Label.text = field3Str;
            code2Label.text =field4Str;
            dateLabel.text = field1Str;

        }
    }

    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

那么在详细信息屏幕中显示所选对象的详细信息的最佳方法是什么

Answer 1

此解决方案适合我

我已将此代码添加到databaseFlipsideViewController

//databaseFlipsideViewController.m

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    if ([segue.identifier isEqualToString:@"showDetail"]) {
        NSIndexPath *indexPath = [self.tableView indexPathForSelectedRow];
        detailController = segue.destinationViewController;
        detailController.customerName = [keys objectAtIndex:indexPath.row];
        NSLog(@"%@", detailController.customerName);
  }
}

我的detailViewController代码是这样的：

@implementation detailViewController

@synthesize customerLabel,code1Label,code2Label,dateLabel,customerName,code1Name;

//file path to database
-(NSString*)filePath {
    NSArray*paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    return [[paths objectAtIndex:0]stringByAppendingPathComponent:@"bp.sql"];
}

//open database
-(void)openDB {

    if(sqlite3_open([[self filePath]UTF8String], &db) !=SQLITE_OK) {
        sqlite3_close(db);
        NSAssert(0, @"Databese failed to open");
    }

    else {
        NSLog(@"database opemed");
    }


}

- (IBAction)back:(id)sender
{
    [self.delegate detailViewControllerDidFinish:self];
}

- (void)viewDidLoad
{

    [self openDB];
    NSString*sql = [NSString stringWithFormat:@"SELECT theDate, customer,code1,code2 FROM summary WHERE key=\"%@\"", customerName];
     const char *query_stmt = [sql UTF8String];
    sqlite3_stmt*statement;

    if (sqlite3_prepare_v2(db, query_stmt, -1, &statement, nil)==SQLITE_OK) {

        if (sqlite3_step(statement)==SQLITE_ROW) {

            NSString *date = [[NSString alloc] initWithUTF8String:(const char *) sqlite3_column_text(statement, 0)];
            dateLabel.text = date;

            NSString *customer = [[NSString alloc] initWithUTF8String:(const char *) sqlite3_column_text(statement, 1)];
            customerLabel.text = customer;

            NSString *code1 = [[NSString alloc] initWithUTF8String:(const char *) sqlite3_column_text(statement, 2)];
            code1Label.text = code1;

            NSString *code2 = [[NSString alloc] initWithUTF8String:(const char *) sqlite3_column_text(statement,3)];
            code2Label.text = code2;

        }
        sqlite3_finalize(statement);

            [super viewDidLoad];
        }
    sqlite3_close(db);
    }

Answer 2

因为- (void)viewDidLoad来自detailViewController您的选择查询未指定用户/摘要，而不是它会选择所有内容。< / p>

在循环中，您将覆盖数据库中每行的所有标签属性。所以结果总是看起来一样，显示数据库的最后一个结果..

答案是实现tableView的didSelectRowAtIndexPath函数，并将用户的ID传递给detailView控制器，然后使用更具体的查询来获取正确的条目，即：

  

@“SELECT * FROM x WHERE id ='％@'”，_ id;

但实际上我认为你需要一个basic lesson SQL ..

Protip：考虑使用Core Data，这是为了这个。当Core Data要限制功能或性能时，你真的只想在你的iPhone上使用SQLite。