[新手学IOS]第六天:持久化应用程序(3)--使用嵌入式SQLite3

使用SQLite3 ,务必要引入 sqlite3包.

关于引入包的方法便不再介绍,直接进入正题:

#import <sqlite3.h>

#define kFilename    @"data.sqlite3"

引入库是很重要的.

下面就是关于 sqlite3的 table的建立,查询,添加数据的操作.如果学习过sql2008 ,那么就很容易理解了.但是还有很多很长的关键词,真的是让我很头疼.\

.h文件和之前的 数据归档相同,就不再赘述了

直接到.m文件吧

#import "BIDViewController.h"
#import <sqlite3.h>

#define kFilename    @"data.sqlite3"

@implementation BIDViewController
@synthesize field1;
@synthesize field2;
@synthesize field3;
@synthesize field4;

- (NSString *)dataFilePath {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(
                                                         NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    return [documentsDirectory stringByAppendingPathComponent:kFilename];
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Release any cached data, images, etc that aren't in use.
}

#pragma mark - View lifecycle

- (void)viewDidLoad
{
    [super viewDidLoad];
	// Do any additional setup after loading the view, typically from a nib.
    sqlite3 *database;
    if (sqlite3_open([[self dataFilePath] UTF8String], &database)
        != SQLITE_OK) {
        sqlite3_close(database);
        NSAssert(0, @"Failed to open database");
    }
    
    // Useful C trivia: If two inline strings are separated by nothing
    // but whitespace (including line breaks), they are concatenated into
    // a single string:
    NSString *createSQL = @"CREATE TABLE IF NOT EXISTS FIELDS "
    "(ROW INTEGER PRIMARY KEY, FIELD_DATA TEXT);";
    char *errorMsg;
    if (sqlite3_exec (database, [createSQL UTF8String],
                      NULL, NULL, &errorMsg) != SQLITE_OK) {
        sqlite3_close(database);
        NSAssert(0, @"Error creating table: %s", errorMsg);
    }
    NSString *query = @"SELECT ROW, FIELD_DATA FROM FIELDS ORDER BY ROW";
    sqlite3_stmt *statement;
    if (sqlite3_prepare_v2(database, [query UTF8String],
                           -1, &statement, nil) == SQLITE_OK) {
        while (sqlite3_step(statement) == SQLITE_ROW) {
            int row = sqlite3_column_int(statement, 0);
            char *rowData = (char *)sqlite3_column_text(statement, 1);
            
            NSString *fieldName = [[NSString alloc]
                                   initWithFormat:@"field%d", row];
            NSString *fieldValue = [[NSString alloc]
                                    initWithUTF8String:rowData];
            UITextField *field = [self valueForKey:fieldName];
            field.text = fieldValue;
        }
        sqlite3_finalize(statement);
    }
    sqlite3_close(database);
    
    UIApplication *app = [UIApplication sharedApplication];
    [[NSNotificationCenter defaultCenter] addObserver:self
        selector:@selector(applicationWillResignActive:)
        name:UIApplicationWillResignActiveNotification
        object:app];
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
    self.field1 = nil;
    self.field2 = nil;
    self.field3 = nil;
    self.field4 = nil;
}

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
}

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];
}

- (void)viewWillDisappear:(BOOL)animated
{
	[super viewWillDisappear:animated];
}

- (void)viewDidDisappear:(BOOL)animated
{
	[super viewDidDisappear:animated];
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    // Return YES for supported orientations
    return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}

- (void)applicationWillResignActive:(NSNotification *)notification {
    sqlite3 *database;
    if (sqlite3_open([[self dataFilePath] UTF8String], &database)
        != SQLITE_OK) {
        sqlite3_close(database);
        NSAssert(0, @"Failed to open database");
    }
    for (int i = 1; i <= 4; i++) {
        NSString *fieldName = [[NSString alloc]
                               initWithFormat:@"field%d", i];
        UITextField *field = [self valueForKey:fieldName];
        
        // Once again, inline string concatenation to the rescue:
        char *update = "INSERT OR REPLACE INTO FIELDS (ROW, FIELD_DATA) "
        "VALUES (?, ?);";
        char *errorMsg;
        sqlite3_stmt *stmt;
        if (sqlite3_prepare_v2(database, update, -1, &stmt, nil)
            == SQLITE_OK) {
            sqlite3_bind_int(stmt, 1, i);
            sqlite3_bind_text(stmt, 2, [field.text UTF8String], -1, NULL);
        }
        if (sqlite3_step(stmt) != SQLITE_DONE)
            NSAssert(0, @"Error updating table: %s", errorMsg);
        sqlite3_finalize(stmt);
        
    }
    sqlite3_close(database);
}