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)";
         
         if (sqlite3_exec(database， sql_stmt， NULL， NULL， &errMsg) != SQLITE_OK) {
            isSuccess = NO;
            NSLog(@"Failed to create table");
         }
         sqlite3_close(database);
         return  isSuccess;
      } else {
         isSuccess = NO;
         NSLog(@"Failed to open/create database");
      }
   }    
   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);
      
      if (sqlite3_step(statement) == SQLITE_DONE) {
         return YES;
      } else {
         return NO;
      }
      sqlite3_reset(statement);
   }
   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];
      
      if (sqlite3_prepare_v2(database， query_stmt， -1， &statement， NULL) == SQLITE_OK) {
         if (sqlite3_step(statement) == SQLITE_ROW) {
            NSString *name = [[NSString alloc] initWithUTF8String:
            (const char *) sqlite3_column_text(statement， 0)];
            [resultArray addObject:name];
            
            NSString *department = [[NSString alloc] initWithUTF8String:
            (const char *) sqlite3_column_text(statement， 1)];
            [resultArray addObject:department];
            
            NSString *year = [[NSString alloc]initWithUTF8String:
            (const char *) sqlite3_column_text(statement， 2)];
            [resultArray addObject:year];
            return resultArray;
         } else {
            NSLog(@"Not found");
            return nil;
         }
         sqlite3_reset(statement);
      }
   }
   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

https://www.learnfk.com/ios/ios-sqlite-database.html