Core Data使用

注意：每次修改CoreData的Attribute时记得把应用给删除重装，要不会崩，因为建立的数据库文件还在该目录下，里面的字段没有更改，所以不能匹配就会崩溃，切忌，要不就每次进来把文件先删除，再建立，不过貌似这样做用户的数据就会丢失，所以还是每次删除应用再装吧。??

1.先建立一个coredata的工程，把Use Core Data勾上

进去后的AppDelegate.m中有如下代码：

#pragma mark - Core Data stack

@synthesize managedObjectContext = _managedObjectContext;
@synthesize managedObjectModel = _managedObjectModel;
@synthesize persistentStoreCoordinator = _persistentStoreCoordinator;
//存储在沙盒里的具体位置- (NSURL *)applicationDocumentsDirectory {
    // The directory the application uses to store the Core Data store file. This code uses a directory named "com.pupuwang.XWClient.CoreDataDemo" in the application‘s documents directory.
    return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject];
}
//托管对象
- (NSManagedObjectModel *)managedObjectModel {
    // The managed object model for the application. It is a fatal error for the application not to be able to find and load its model.
    if (_managedObjectModel != nil) {
        return _managedObjectModel;
    }
    NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"CoreDataDemo" withExtension:@"momd"];
    _managedObjectModel = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
    return _managedObjectModel;
}
//持久化存储协调器
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator {
    // The persistent store coordinator for the application. This implementation creates and return a coordinator, having added the store for the application to it.
    if (_persistentStoreCoordinator != nil) {
        return _persistentStoreCoordinator;
    }

    // Create the coordinator and store

    _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
    NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"CoreDataDemo.sqlite"];
    NSError *error = nil;
    NSString *failureReason = @"There was an error creating or loading the application‘s saved data.";
    if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
        // Report any error we got.
        NSMutableDictionary *dict = [NSMutableDictionary dictionary];
        dict[NSLocalizedDescriptionKey] = @"Failed to initialize the application‘s saved data";
        dict[NSLocalizedFailureReasonErrorKey] = failureReason;
        dict[NSUnderlyingErrorKey] = error;
        error = [NSError errorWithDomain:@"YOUR_ERROR_DOMAIN" code:9999 userInfo:dict];
        // Replace this with code to handle the error appropriately.
        // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
        NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
        abort();
    }

    return _persistentStoreCoordinator;
}

//托管上下文
- (NSManagedObjectContext *)managedObjectContext {
    // Returns the managed object context for the application (which is already bound to the persistent store coordinator for the application.)
    if (_managedObjectContext != nil) {
        return _managedObjectContext;
    }

    NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
    if (!coordinator) {
        return nil;
    }
    _managedObjectContext = [[NSManagedObjectContext alloc] init];
    [_managedObjectContext setPersistentStoreCoordinator:coordinator];
    return _managedObjectContext;
}

#pragma mark - Core Data Saving support

- (void)saveContext {
    NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
    if (managedObjectContext != nil) {
        NSError *error = nil;
        if ([managedObjectContext hasChanges] && ![managedObjectContext save:&error]) {
            // Replace this implementation with code to handle the error appropriately.
            // abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
            NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
            abort();
        }
    }
}

自己手动建立起来coredata文件，也可以自己手动写

2.建立实体

选中xcdatamodeld后缀文件，按下面步骤操作：

选中xcdatamodeld后缀文件，点击导航栏Editor->Create NSManagedObject Subclass 一路next，建立模型对象User.h User.m

其中生成的model：User里面的属性用的是@dynamic

@property有两个对应的词，一个是@synthesize，一个是@dynamic。如果@synthesize和@dynamic都没写，那么默认的就是@syntheszie var = _var;

@synthesize的语义是如果你没有手动实现setter方法和getter方法，那么编译器会自动为你加上这两个方法。

@dynamic告诉编译器,属性的setter与getter方法由用户自己实现，不自动生成。（当然对于readonly的属性只需提供getter即可）。假如一个属性被声明为@dynamic var，然后你没有提供@setter方法和@getter方法，编译的时候没问题，但是当程序运行到instance.var =someVar，由于缺setter方法会导致程序崩溃；或者当运行到 someVar = var时，由于缺getter方法同样会导致崩溃。编译时没问题，运行时才执行相应的方法，这就是所谓的动态绑定。

3.APPDelegate.m中

_window = [[UIWindow alloc]initWithFrame:[UIScreen mainScreen].bounds];
View1Controller *view1 = [[View1Controller alloc]init];
view1.myAppdelegate = self;
_window.rootViewController = view1;
[_window makeKeyAndVisible];

4.View1Controller.h中

#import <UIKit/UIKit.h>
#import <CoreData/CoreData.h>
#import "AppDelegate.h"
#import "User.h"

@interface View1Controller : UIViewController
@property (nonatomic,strong) AppDelegate *myAppdelegate;//创建该视图的记得把值传过来
@end

5.View1Controller.m中

#import "View1Controller.h"

@interface View1Controller ()<UITextFieldDelegate>
@property (weak, nonatomic) IBOutlet UITextField *nameTF;
@property (weak, nonatomic) IBOutlet UITextField *ageTF;
@property (weak, nonatomic) IBOutlet UITextField *sexTF;
@property (weak, nonatomic) IBOutlet UITextView *serchContent;

@end

@implementation View1Controller

- (void)viewDidLoad {
    [super viewDidLoad];

    // Do any additional setup after loading the view, typically from a nib.
}

#pragma mark - Click
//保存数据
- (IBAction)saveData:(id)sender {
    User *user = (User *)[NSEntityDescription insertNewObjectForEntityForName:@"User" inManagedObjectContext:self.myAppdelegate.managedObjectContext];
    [user setName:self.nameTF.text];
    [user setAge:@([self.ageTF.text integerValue])];
    [user setSex:self.sexTF.text];
    [user setBirth:[NSDate dateWithTimeIntervalSinceNow:100000]];
    [self saveStatus];
}//查询数据
- (IBAction)serchData:(id)sender {
    NSFetchRequest *request = [[NSFetchRequest alloc]init];
    NSEntityDescription *user = [NSEntityDescription entityForName:@"User" inManagedObjectContext:self.myAppdelegate.managedObjectContext];
    [request setEntity:user];
    NSError *error;
    NSArray *mutablefetchResult = [self.myAppdelegate.managedObjectContext executeFetchRequest:request error:&error];
    if (mutablefetchResult == nil) {
        NSLog(@"Seach fail");
    }
    NSLog(@"coredata entity count is %ld",[mutablefetchResult count]);
    NSMutableString *string = [[NSMutableString alloc]init];
    for (User *user in mutablefetchResult) {
        [string appendFormat:@"name = %@,age = %@,sex = %@,birthDay = %@",user.name,user.age,user.sex,user.birth];
        [string appendFormat:@"\n"];
    }
    self.serchContent.text = string;
}
//更新数据
- (IBAction)updateData:(id)sender {
    NSFetchRequest *request  =[[NSFetchRequest alloc]init];
    NSEntityDescription *user = [NSEntityDescription entityForName:@"User" inManagedObjectContext:self.myAppdelegate.managedObjectContext];
    [request setEntity:user];
    NSError *error;
    //设置查询条件 NSPredicate （谓词）：查询语句
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name = %@",self.nameTF.text];
    [request setPredicate:predicate];

    NSArray *mutabelFetchResult = [self.myAppdelegate.managedObjectContext executeFetchRequest:request error:&error];
    if (mutabelFetchResult == nil) {
        NSLog(@"seach fail");
    }
    NSLog(@"coredata entity count is %ld",mutabelFetchResult.count);
    for (User *user in mutabelFetchResult) {
        [user setAge:@([self.ageTF.text integerValue])];
    }
    [self saveStatus];
}//删除数据
- (IBAction)cancelData:(id)sender {
    NSFetchRequest *request = [[NSFetchRequest alloc]init];
    NSEntityDescription *user = [NSEntityDescription entityForName:@"User" inManagedObjectContext:self.myAppdelegate.managedObjectContext];
    [request setEntity:user];
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name = %@",self.nameTF.text];
    [request setPredicate:predicate];

    NSError *error;
    NSArray *mutableFetchResult = [self.myAppdelegate.managedObjectContext executeFetchRequest:request error:&error];
    if (mutableFetchResult == nil) {
        NSLog(@"search fail");
    }
    NSLog(@"coredata entity count is %ld",mutableFetchResult.count);

    for (User *user in mutableFetchResult) {
        [self.myAppdelegate.managedObjectContext deleteObject:user];
    }
    [self saveStatus];
}
//数据是否保存成功
- (void)saveStatus{
    NSError *error;
    BOOL isSuccess = [self.myAppdelegate.managedObjectContext save:&error];
    if (!isSuccess) {
        NSLog(@"save fail");
    }else{
        NSLog(@"save success");
    }
}

-(BOOL)textFieldShouldReturn:(UITextField *)textField{
    [textField resignFirstResponder];
    return YES;

}