我正在构建一个包含一个视图中的表单的应用程序，其中用户填充所有字段，当他单击保存按钮时，数据必须保存到数据库中，并且在导航回来之后，还有另一个视图，当输入后，必须显示已保存的数据（事件）。
我创建了一个数据库，并经历了几个sqlite3教程;
我已根据我的要求对代码进行了所有其他更改。但是，当我使用此语句检查数据是否插入数据库时：
SELECT * FROM reminders;
我什么都没得到，我对是否插入数据感到困惑。
如何正确保存，如何从数据库中检索数据并在其他视图中显示？
答案 0 :(得分：4)
首先，您应该创建sqlite3数据库文件（check this link），然后将其包含在项目中。现在要连接到它，您可以使用以下代码：
#pragma mark -
#pragma mark Create/Load Database
+ (void)createEditableCopyOfDatabaseIfNeeded {
// First, test for existence.
NSArray * paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString * documentsDirectory = [paths objectAtIndex:0];
NSString * writableDBPath = [documentsDirectory stringByAppendingPathComponent:@"DATABASENAME.DB"];
BOOL success;
NSFileManager * fileManager = [NSFileManager defaultManager];
success = [fileManager fileExistsAtPath:writableDBPath];
if (success) {
return;
}
// The writable database does not exist, so copy the default to the appropriate location.
NSError * error;
NSString * defaultDBPath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"DATABASENAME.DB"];
success = [fileManager copyItemAtPath:defaultDBPath toPath:writableDBPath error:&error];
if (!success) {
NSAssert1(0, @"Failed to create writable database file with message '%@'.", [error localizedDescription]);
}
}
+ (sqlite3 *)getDBConnection {
[DatabaseController createEditableCopyOfDatabaseIfNeeded];
NSArray * paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString * documentsDirectory = [paths objectAtIndex:0];
NSString * path = [documentsDirectory stringByAppendingPathComponent:@"DATABASENAME.DB"];
// Open the database. The database was prepared outside the application.
sqlite3 * newDBConnection;
if (sqlite3_open([path UTF8String], &newDBConnection) == SQLITE_OK) {
//NSLog(@"Database Successfully Opened :)");
} else {
//NSLog(@"Error in opening database :(");
}
return newDBConnection;
}
然后插入记录即可使用此代码：
+ (void)insertEvent:(Event *)newEvent {
sqlite3 * connection = [DatabaseController getDBConnection];
const char * text = "INSERT INTO Event (Serial, Name, Date) VALUES (?, ?, ?)";
sqlite3_stmt * insert_statement;
int prepare_result = sqlite3_prepare_v2(connection, text, -1, &insert_statement, NULL);
if ((prepare_result != SQLITE_DONE) && (prepare_result != SQLITE_OK)) {
// Error
sqlite3_close(connection);
return;
}
sqlite3_bind_int(insert_statement, 1, newEvent.Serial);
sqlite3_bind_text(insert_statement, 2, [newEvent.Name UTF8String], -1, SQLITE_TRANSIENT);
sqlite3_bind_double(insert_statement, 3, [newEvent.Date timeIntervalSince1970]);
int statement_result = sqlite3_step(insert_statement);
if ((statement_result != SQLITE_DONE) && (statement_result != SQLITE_OK)) {
//Error
sqlite3_close(connection);
return;
}
sqlite3_finalize(insert_statement);
// Get the Id of the inserted event
int rowId = sqlite3_last_insert_rowid(connection);
newEvent.Id = rowId;
sqlite3_close(connection);
}
现在要举办活动：
+ (Event *)getEventById:(int)id {
Event * result = nil;
sqlite3 * connection = [DatabaseController getDBConnection];
const char * text = "SELECT * FROM Event WHERE Id = ?";
sqlite3_stmt * select_statement;
int prepare_result = sqlite3_prepare_v2(connection, text, -1, &select_statement, NULL);
if ((prepare_result != SQLITE_DONE) && (prepare_result != SQLITE_OK)) {
// error
sqlite3_close(connection);
return result;
}
sqlite3_bind_int(select_statement, 1, id);
if (sqlite3_step(select_statement) == SQLITE_ROW) {
result = [[[Event alloc] init] autorelease];
result.Id = sqlite3_column_int(select_statement, 0);
result.Serial = sqlite3_column_int(select_statement, 1);
result.Name = (((char *) sqlite3_column_text(select_statement, 2)) == NULL)? nil:[NSString stringWithUTF8String:((char *) sqlite3_column_text(select_statement, 2))];
result.Date = [NSDate dateWithTimeIntervalSince1970:sqlite3_column_double(select_statement, 3)];
}
sqlite3_finalize(select_statement);
sqlite3_close(connection);
return (result);
}
答案 1 :(得分：1)
这是一篇博文，应该让你指出正确的方向，对我来说非常有用，所以与你分享。：P
答案 2 :(得分：1)
您可以通过检查数据库表来检查您的数据是否已保存。转到用户＆gt;您的计算机名称＆gt;库＆gt;应用程序支持＆gt; iphone模拟器＆gt; 4.3（您的ios版本）＆gt;应用程序..然后查找您的应用程序，转到文档并打开sqlite文件。在这里你可以看到数据。
答案 3 :(得分：0)
答案 4 :(得分：0)
此代码用于存储数据并从sqlite数据库中检索数据 首先，您只需在objective-c
中编写下面的代码后添加sqlite3框架工作ViewController.h
#import <UIKit/UIKit.h>
#import "sqlite3.h"
@interface ViewController : UIViewController
@property (weak, nonatomic) IBOutlet UITextField *firstName;
@property (weak, nonatomic) IBOutlet UITextField *lastName;
@property (weak, nonatomic) IBOutlet UITextField *state;
@property (weak, nonatomic) IBOutlet UITextField *mobileNum;
- (IBAction)saveButton:(id)sender;
- (IBAction)featchButton:(id)sender;
@property (weak, nonatomic) IBOutlet UILabel *label;
@property NSString *myDatabase;
@property sqlite3 *marksDB;
ViewController.m
#import "ViewController.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
NSString *docsDir;
NSArray *dirPaths;
dirPaths=NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
docsDir=dirPaths[0];
_myDatabase=[[NSString alloc]initWithString:[docsDir stringByAppendingString:@"marks.db"]];
NSLog(@"My Data base %@",_myDatabase);
NSFileManager *fileMgr=[NSFileManager defaultManager];
if ([fileMgr fileExistsAtPath:_myDatabase]==NO)
{
const char *dbpath=[_myDatabase UTF8String];
if (sqlite3_open(dbpath, &_marksDB)==SQLITE_OK)
{
char *errMsg;
const char *sql_stmt="CREATE TABLE IF NOT EXISTS MARKS(ID INTEGER PRIMARY KEY AUTOINCREMENT ,FIRST NAME TEXT,LAST NAME TEXT,STATE TEXT,MOBILE INTEGER )";
if (sqlite3_exec(_marksDB, sql_stmt, NULL, NULL, &errMsg)!=SQLITE_OK)
{
_label.text=@"Failed to create Table";
}
sqlite3_close(_marksDB);
}
else
{
_label.text=@"Failed to Create/Open Database";
}
}
}
- (IBAction)saveButton:(id)sender {
sqlite3_stmt *statement;
const char *dbpath=[_myDatabase UTF8String];
if (sqlite3_open(dbpath, &_marksDB)==SQLITE_OK)
{
NSString *insertSQL=[NSString stringWithFormat:@"INSERT INTO MARKS(firstname,lastname,state,mobile )VALUES(\"%@\",\"%@\",\"%@\",\"%@\")",_firstName.text,_lastName.text,_state.text,_mobileNum.text ];
const char *insert_stmt=[insertSQL UTF8String];
sqlite3_prepare_v2(_marksDB, insert_stmt, -1, &statement, NULL);
if (sqlite3_step(statement)==SQLITE_DONE)
{
_label.text=@"Contact Added";
_firstName.text=@"";
_lastName.text=@"";
_state.text=@"";
_mobileNum.text=@"";
}
else
{
_label.text=@"Failed to Add Contact";
}
sqlite3_finalize(statement);
sqlite3_close(_marksDB);
}
}
- (IBAction)featchButton:(id)sender {
const char *dbpath=[_myDatabase UTF8String];
sqlite3_stmt *statement;
if (sqlite3_open(dbpath, &_marksDB)==SQLITE_OK)
{
NSString *query=[NSString stringWithFormat:@"SELECT firstname,lastname,state,mobile, FROM MARKS WHERE firstname=\"%@\"",_firstName.text];
const char *query_stmt=[query UTF8String];
if (sqlite3_prepare_v2(_marksDB, query_stmt, -1, &statement, NULL)==SQLITE_OK)
{
if (sqlite3_step(statement)==SQLITE_ROW)
{
NSString *first=[[NSString alloc]initWithUTF8String:(const char *)sqlite3_column_text(statement, 0)];
_firstName.text=first;
NSString *lastName=[[NSString alloc]initWithUTF8String:(const char *)sqlite3_column_text(statement, 1)];
_lastName.text=lastName;
NSString *state=[[NSString alloc]initWithUTF8String:(const char *)sqlite3_column_text(statement, 2)];
_state.text=state;
NSString *mobile=[[NSString alloc]initWithUTF8String:(const char *)sqlite3_column_text(statement, 3)];
_mobileNum.text=mobile;
_label.text=@"Match Found";
}
else
{
_label.text=@"Not Matched";
_lastName.text=@"";
_state.text=@"";
_mobileNum.text=@"";
}
sqlite3_finalize(statement);
}
sqlite3_close(_marksDB);
}
}
@end