无涯教程-OC - SQLite

SQLite可以在iOS中用于处理数据。它使用sqlite查询，这对于那些了解SQL的人来说更加容易。

涉及步骤

步骤1 - 创建一个简单的基于视图的应用程序。

步骤2 - 选择您的项目文件，然后选择目标，然后在选择框架中添加 libsqlite3.dylib 库。

步骤3 - 选择"File"→"New"→"File..."，然后选择"Objective C class" ，然后单击"Next"。

步骤4 - 将类命名为 DBManager ，将" sub class of"作为NSObject。

步骤5 - 选择创建。

步骤6 - 如下更新 DBManager.h -

#import <Foundation/Foundation.h>
#import <sqlite3.h>
@interface DBManager : NSObject {
NSString *databasePath;
}
+(DBManager)getSharedInstance;
-(BOOL)createDB;
-(BOOL) saveData:(NSString)registerNumber name:(NSString)name
department:(NSString)department year:(NSString)year;
-(NSArray) findByRegisterNumber:(NSString*)registerNumber;
@end

步骤7 - 如下更新 DBManager.m -

#import "DBManager.h"
static DBManager *sharedInstance = nil;
static sqlite3 *database = nil;
static sqlite3_stmt *statement = nil;
@implementation DBManager
+(DBManager*)getSharedInstance {
if (!sharedInstance) {
sharedInstance = [[super allocWithZone:NULL]init];
[sharedInstance createDB];
}
return sharedInstance;
}
-(BOOL)createDB {
NSString docsDir;
NSArray dirPaths;
//Get the documents directory
dirPaths = NSSearchPathForDirectoriesInDomains
(NSDocumentDirectory， NSUserDomainMask， YES);
docsDir = dirPaths[0];
//Build the path to the database file
databasePath = [[NSString alloc] initWithString:
[docsDir stringByAppendingPathComponent: @"student.db"]];
BOOL isSuccess = YES;
NSFileManager *filemgr = [NSFileManager defaultManager];
if ([filemgr fileExistsAtPath: databasePath ] == NO) {
const char dbpath = [databasePath UTF8String];
if (sqlite3_open(dbpath， &database) == SQLITE_OK) {
char errMsg;
const char *sql_stmt =
"create table if not exists studentsDetail (regno integer
primary key， name text， department text， year text)";
     </span><span class="kwd">if</span><span class="pln"> </span><span class="pun">(</span><span class="pln">sqlite3_exec</span><span class="pun">(</span><span class="pln">database</span><span class="pun">，</span><span class="pln"> sql_stmt</span><span class="pun">，</span><span class="pln"> NULL</span><span class="pun">，</span><span class="pln"> NULL</span><span class="pun">，</span><span class="pln"> </span><span class="pun">&amp;</span><span class="pln">errMsg</span><span class="pun">)</span><span class="pln"> </span><span class="pun">!=</span><span class="pln"> SQLITE_OK</span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
        isSuccess </span><span class="pun">=</span><span class="pln"> NO</span><span class="pun">;</span><span class="pln">
        </span><span class="typ">NSLog</span><span class="pun">(@</span><span class="str">"Failed to create table"</span><span class="pun">);</span><span class="pln">
     </span><span class="pun">}</span><span class="pln">
     sqlite3_close</span><span class="pun">(</span><span class="pln">database</span><span class="pun">);</span><span class="pln">
     </span><span class="kwd">return</span><span class="pln">  isSuccess</span><span class="pun">;</span><span class="pln">
  </span><span class="pun">}</span><span class="pln"> </span><span class="kwd">else</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
     isSuccess </span><span class="pun">=</span><span class="pln"> NO</span><span class="pun">;</span><span class="pln">
     </span><span class="typ">NSLog</span><span class="pun">(@</span><span class="str">"Failed to open/create database"</span><span class="pun">);</span><span class="pln">
  </span><span class="pun">}</span><span class="pln">

}

return isSuccess;
}
- (BOOL) saveData:(NSString)registerNumber name:(NSString)name
department:(NSString)department year:(NSString)year; {
const char *dbpath = [databasePath UTF8String];
if (sqlite3_open(dbpath， &database) == SQLITE_OK) {
NSString insertSQL = [NSString stringWithFormat:@"insert into
studentsDetail (regno，name， department， year) values
("%d"，"%@"，"%@"，"%@")"，[registerNumber integerValue]，
name， department， year];

const char insert_stmt = [insertSQL UTF8String];
sqlite3_prepare_v2(database， insert_stmt，-1， &statement， NULL);
  </span><span class="kwd">if</span><span class="pln"> </span><span class="pun">(</span><span class="pln">sqlite3_step</span><span class="pun">(</span><span class="pln">statement</span><span class="pun">)</span><span class="pln"> </span><span class="pun">==</span><span class="pln"> SQLITE_DONE</span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
     </span><span class="kwd">return</span><span class="pln"> YES</span><span class="pun">;</span><span class="pln">
  </span><span class="pun">}</span><span class="pln"> </span><span class="kwd">else</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
     </span><span class="kwd">return</span><span class="pln"> NO</span><span class="pun">;</span><span class="pln">
  </span><span class="pun">}</span><span class="pln">
  sqlite3_reset</span><span class="pun">(</span><span class="pln">statement</span><span class="pun">);</span><span class="pln">

}
return NO;
}
- (NSArray) findByRegisterNumber:(NSString)registerNumber {
const char *dbpath = [databasePath UTF8String];
if (sqlite3_open(dbpath， &database) == SQLITE_OK) {
NSString querySQL = [NSString stringWithFormat:
@"select name， department， year from studentsDetail where
regno="%@""，registerNumber];
const char query_stmt = [querySQL UTF8String];
NSMutableArray *resultArray = [[NSMutableArray alloc]init];
  </span><span class="kwd">if</span><span class="pln"> </span><span class="pun">(</span><span class="pln">sqlite3_prepare_v2</span><span class="pun">(</span><span class="pln">database</span><span class="pun">，</span><span class="pln"> query_stmt</span><span class="pun">，</span><span class="pln"> </span><span class="pun">-</span><span class="lit">1</span><span class="pun">，</span><span class="pln"> </span><span class="pun">&amp;</span><span class="pln">statement</span><span class="pun">，</span><span class="pln"> NULL</span><span class="pun">)</span><span class="pln"> </span><span class="pun">==</span><span class="pln"> SQLITE_OK</span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
     </span><span class="kwd">if</span><span class="pln"> </span><span class="pun">(</span><span class="pln">sqlite3_step</span><span class="pun">(</span><span class="pln">statement</span><span class="pun">)</span><span class="pln"> </span><span class="pun">==</span><span class="pln"> SQLITE_ROW</span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
        </span><span class="typ">NSString</span><span class="pln"> </span><span class="pun">*</span><span class="pln">name </span><span class="pun">=</span><span class="pln"> </span><span class="pun">[[</span><span class="typ">NSString</span><span class="pln"> alloc</span><span class="pun">]</span><span class="pln"> initWithUTF8String</span><span class="pun">:</span><span class="pln">
        </span><span class="pun">(</span><span class="kwd">const</span><span class="pln"> </span><span class="kwd">char</span><span class="pln"> </span><span class="pun">*)</span><span class="pln"> sqlite3_column_text</span><span class="pun">(</span><span class="pln">statement</span><span class="pun">，</span><span class="pln"> </span><span class="lit">0</span><span class="pun">)];</span><span class="pln">
        </span><span class="pun">[</span><span class="pln">resultArray addObject</span><span class="pun">:</span><span class="pln">name</span><span class="pun">];</span><span class="pln">
        
        </span><span class="typ">NSString</span><span class="pln"> </span><span class="pun">*</span><span class="pln">department </span><span class="pun">=</span><span class="pln"> </span><span class="pun">[[</span><span class="typ">NSString</span><span class="pln"> alloc</span><span class="pun">]</span><span class="pln"> initWithUTF8String</span><span class="pun">:</span><span class="pln">
        </span><span class="pun">(</span><span class="kwd">const</span><span class="pln"> </span><span class="kwd">char</span><span class="pln"> </span><span class="pun">*)</span><span class="pln"> sqlite3_column_text</span><span class="pun">(</span><span class="pln">statement</span><span class="pun">，</span><span class="pln"> </span><span class="lit">1</span><span class="pun">)];</span><span class="pln">
        </span><span class="pun">[</span><span class="pln">resultArray addObject</span><span class="pun">:</span><span class="pln">department</span><span class="pun">];</span><span class="pln">
        
        </span><span class="typ">NSString</span><span class="pln"> </span><span class="pun">*</span><span class="pln">year </span><span class="pun">=</span><span class="pln"> </span><span class="pun">[[</span><span class="typ">NSString</span><span class="pln"> alloc</span><span class="pun">]</span><span class="pln">initWithUTF8String</span><span class="pun">:</span><span class="pln">
        </span><span class="pun">(</span><span class="kwd">const</span><span class="pln"> </span><span class="kwd">char</span><span class="pln"> </span><span class="pun">*)</span><span class="pln"> sqlite3_column_text</span><span class="pun">(</span><span class="pln">statement</span><span class="pun">，</span><span class="pln"> </span><span class="lit">2</span><span class="pun">)];</span><span class="pln">
        </span><span class="pun">[</span><span class="pln">resultArray addObject</span><span class="pun">:</span><span class="pln">year</span><span class="pun">];</span><span class="pln">
        </span><span class="kwd">return</span><span class="pln"> resultArray</span><span class="pun">;</span><span class="pln">
     </span><span class="pun">}</span><span class="pln"> </span><span class="kwd">else</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
        </span><span class="typ">NSLog</span><span class="pun">(@</span><span class="str">"Not found"</span><span class="pun">);</span><span class="pln">
        </span><span class="kwd">return</span><span class="pln"> </span><span class="kwd">nil</span><span class="pun">;</span><span class="pln">
     </span><span class="pun">}</span><span class="pln">
     sqlite3_reset</span><span class="pun">(</span><span class="pln">statement</span><span class="pun">);</span><span class="pln">
  </span><span class="pun">}</span><span class="pln">

}
return nil;
}

步骤8 - 如下更新 ViewController.xib 文件-

步骤9 - 为上述文本字段创建IBOutlet。

步骤10 - 为上述按钮创建IBAction。

步骤11 - 如下更新 ViewController.h -

#import <UIKit/UIKit.h>
#import "DBManager.h"
@interface ViewController : UIViewController<UITextFieldDelegate> {
IBOutlet UITextField regNoTextField;
IBOutlet UITextField nameTextField;
IBOutlet UITextField departmentTextField;
IBOutlet UITextField yearTextField;
IBOutlet UITextField findByRegisterNumberTextField;
IBOutlet UIScrollView myScrollView;
}
-(IBAction)saveData:(id)sender;
-(IBAction)findData:(id)sender;
@end

步骤12 - 如下更新 ViewController.m -

#import "ViewController.h"
@interface ViewController ()
@end
@implementation ViewController
- (id)initWithNibName:(NSString )nibNameOrNil bundle:(NSBundle )
nibBundleOrNil {
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
//Custom initialization
}
return self;
}
- (void)viewDidLoad {
[super viewDidLoad];
//Do any additional setup after loading the view from its nib.
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
//Dispose of any resources that can be recreated.
}
-(IBAction)saveData:(id)sender {
BOOL success = NO;
NSString *alertString = @"Data Insertion failed";
if (regNoTextField.text.length>0 &&nameTextField.text.length>0 &&
departmentTextField.text.length>0 &&yearTextField.text.length>0 ) {
success = [[DBManager getSharedInstance]saveData:
regNoTextField.text name:nameTextField.text department:
departmentTextField.text year:yearTextField.text];
} else {
alertString = @"Enter all fields";
}
if (success == NO) {
UIAlertView *alert = [[UIAlertView alloc]initWithTitle:
alertString message:nil
delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
[alert show];
}
}
-(IBAction)findData:(id)sender {
NSArray *data = [[DBManager getSharedInstance]findByRegisterNumber:
findByRegisterNumberTextField.text];
if (data == nil) {
UIAlertView *alert = [[UIAlertView alloc]initWithTitle:
@"Data not found" message:nil delegate:nil cancelButtonTitle:
@"OK" otherButtonTitles:nil];
[alert show];
regNoTextField.text = @"";
nameTextField.text =@"";
departmentTextField.text = @"";
yearTextField.text =@"";
} else {
regNoTextField.text = findByRegisterNumberTextField.text;
nameTextField.text =[data objectAtIndex:0];
departmentTextField.text = [data objectAtIndex:1];
yearTextField.text =[data objectAtIndex:2];
}
}
#pragma mark - Text field delegate
-(void)textFieldDidBeginEditing:(UITextField *)textField {
[myScrollView setFrame:CGRectMake(10， 50， 300， 200)];
[myScrollView setContentSize:CGSizeMake(300， 350)];
}
-(void)textFieldDidEndEditing:(UITextField *)textField {
[myScrollView setFrame:CGRectMake(10， 50， 300， 350)];
}
-(BOOL) textFieldShouldReturn:(UITextField *)textField {
[textField resignFirstResponder];
return YES;
}
@end

运行应用程序时，无涯教程将获得以下输出，无涯教程可以在其中添加并找到学生详细信息-

参考链接

www.learnfk.com/ios/ios-sql…