📜  iOS-SQLite数据库

📅  最后修改于: 2020-12-08 06:21:35             🧑  作者: Mango


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。

涉及的步骤

步骤1-创建一个简单的基于View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-通过选择文件→新建→文件…→选择Objective C类来创建一个新文件,然后单击下一步。

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 
#import 

@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-更新DBManager.m ,如下所示-

#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-更新ViewController.xib文件,如下所示:

iOS教程

步骤9-为上述文本字段创建IBOutlets。

步骤10-为上述按钮创建IBAction。

步骤11-更新ViewController.h ,如下所示:

#import 
#import "DBManager.h"

@interface ViewController : UIViewController {
   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-更新ViewController.m如下-

#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

输出

运行应用程序时,我们将获得以下输出,我们可以在其中添加并找到学生详细信息-

iOS教程