NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = paths[0];

NSString *filename = [documentsDirectory stringByAppendingPathComponent:@”theFile.txt”];

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES);
NSString *libraryDirectory = paths[0];

NSString *tempPath = NSTemporaryDirectory();
NSString *filename = [tempPath stringByAppendingPathComponent:@”theFile.txt”];

[myArray writeToFile:@”/some/file/location/output.plist” atomically:YES];

@interface PlistViewController ()
- (IBAction)saveClicked:(id)sender;
@property (strong, nonatomic) IBOutletCollection(UITextField) NSArray *lineFields;

@end

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    NSString *filePath = [self dataFilePath];
    if ([[NSFileManager defaultManager] fileExistsAtPath:filePath]) {
        NSArray *array = [[NSArray alloc] initWithContentsOfFile:filePath];
        for (int i = 0; i < 4; i++) {
            UITextField *theField = self.lineFields[i];
            theField.text = array[i];
        }
    }
}

-(NSString *)dataFilePath{
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    return [documentsDirectory stringByAppendingPathComponent:@"data.plist"];
}

- (IBAction)saveClicked:(id)sender {
    NSString *filePath = [self dataFilePath];
    NSArray *array = [self.lineFields valueForKey:@"text"];
    [array writeToFile:filePath atomically:YES];
}

-(void)encodeWithCoder: (NSCoder *)encoder;

-(id)initWithCoder: (NSCoder *)decoder;

#import "ArchiverViewController.h"
#import "Lines.h"

static NSString *const kRootKey = @"kRootKey";

@interface ArchiverViewController ()
- (IBAction)saveClicked:(id)sender;
@property (strong, nonatomic) IBOutletCollection(UITextField) NSArray *lineFields;

@end

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    NSString *filePath = [self dataFilePath];
    if ([[NSFileManager defaultManager] fileExistsAtPath:filePath]) {
        NSData *data = [[NSMutableData alloc] initWithContentsOfFile:filePath];
        NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
        Lines *lines = [unarchiver decodeObjectForKey:kRootKey];
        [unarchiver finishDecoding];
        
        for (int i = 0; i < 4; i++) {
            UITextField *theField = self.lineFields[i];
            theField.text = lines.lines[i];
        }
    }
}

-(NSString *)dataFilePath{
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    return [documentsDirectory stringByAppendingPathComponent:@"data.archive"];
}

- (IBAction)saveClicked:(id)sender {
    NSString *filePath = [self dataFilePath];
    Lines *lines = [[Lines alloc] init];
    lines.lines = [self.lineFields valueForKey:@"text"];
    NSMutableData *data = [[NSMutableData alloc] init];
    NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
    [archiver encodeObject:lines forKey:kRootKey];
    [archiver finishEncoding];
    [data writeToFile:filePath atomically:YES];
}

/*将整型数据绑定到第一个变量，将字符串绑定到第二个变量，然后执行并结束语句*/
char *sql = “insert into foo values (?, ?);”;
sqlite3_stmt *stmt;

if(sqlite3_prepare_v2(database, sql, -1, &stmt, nil) == SQLITE_OK){
    sqlite3_bind_int(stmt, 1, 235);
    sqlite3_bind_text(stmt, 2, “Bar”, -1, NULL);
}

if(sqlite3_step(stmt) != SQLITE_DONE){
    NSLog(@”This should be real error checking!”);
}

sqlite3_finalize(stmt);

#import "SqliteViewController.h"
#import <sqlite3.h>

@interface SqliteViewController ()
- (IBAction)saveClicked:(id)sender;
@property (strong, nonatomic) IBOutletCollection(UITextField) NSArray *lineFields;

@end

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    sqlite3 *database;
    //打开数据库
    if (sqlite3_open([[self dataFilePath] UTF8String], &database) != SQLITE_OK) {
        sqlite3_close(database);
        NSAssert(0, @"Failed to open database");
    }
    
    /**
     有用的C语言知识：
     如果两个内联的字符串之间只有空白（包括换行符）而没有其他字符，
     那么这两个字符串会被连接为一个字符串。
     */
    
    //创建数据库SQL
    NSString *createSQL = @"create table if not exists fields (row integer primary key, field_data text);";
    char *errorMsg;
    //执行SQL语句
    if (sqlite3_exec(database, [createSQL UTF8String], NULL, NULL, &errorMsg) != SQLITE_OK) {
        sqlite3_close(database);
        NSAssert(0, @"Error creating table: %s", errorMsg);
    }
    
    //查询数据库
    NSString *query = @"select row, field_data from fields order by row;";
    sqlite3_stmt *statement;
    if (sqlite3_prepare_v2(database, [query UTF8String], -1, &statement, nil) == SQLITE_OK) {
        //遍历返回的每行
        while (sqlite3_step(statement) == SQLITE_ROW) {
            int row = sqlite3_column_int(statement, 0);
            char *rowData = (char *)sqlite3_column_text(statement, 1);
            NSString *fieldValue = [[NSString alloc] initWithUTF8String:rowData];
            UITextField *field = self.lineFields[row];
            field.text = fieldValue;
        }
        sqlite3_finalize(statement);
    }
    //关闭数据库
    sqlite3_close(database);
}

-(NSString *)dataFilePath{
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    return [documentsDirectory stringByAppendingPathComponent:@"data.sqlite"];
}

- (IBAction)saveClicked:(id)sender {
    sqlite3 *database;
    if (sqlite3_open([[self dataFilePath] UTF8String], &database) != SQLITE_OK) {
        sqlite3_close(database);
        NSAssert(0, @"Failed to open database");
    }
    
    for (int i = 0; i < 4; i++) {
        UITextField *field = self.lineFields[i];
        //内联字符串的连接，又一次派上用场
        char *update = "insert or replace into fields (row, field_data) values (?, ?);";
        char *errorMsg = NULL;
        sqlite3_stmt *stmt;
        //绑定变量
        if (sqlite3_prepare_v2(database, update, -1, &stmt, nil) == SQLITE_OK) {
            sqlite3_bind_int(stmt, 1, i);
            sqlite3_bind_text(stmt, 2, [field.text UTF8String], -1, NULL);
        }
        //判断执行更新是否成功
        if (sqlite3_step(stmt) != SQLITE_DONE) {
            NSAssert(0, @"Error updating table: %s", errorMsg);
        }
        sqlite3_finalize(stmt);
    }
    sqlite3_close(database);
}

#import "CoreDataViewController.h"
#import <CoreData/CoreData.h>

static NSString *const kLineEntityName = @"Line";
static NSString *const kLineNumberKey = @"lineNumber";
static NSString *const kLineTextKey = @"lineText";

@interface CoreDataViewController ()
- (IBAction)saveClicked:(id)sender;
@property (strong, nonatomic) IBOutletCollection(UITextField) NSArray *lineFields;

@end

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    NSManagedObjectContext *context = [self myContext];

    NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:kLineEntityName];
    NSError *error;
    NSArray *objects = [context executeFetchRequest:request error:&error];
    if (objects == nil) {
        NSLog(@"There was an error!");
    }

    for (NSManagedObject *oneObject in objects) {
        int lineNum = [[oneObject valueForKey:kLineNumberKey] intValue];
        NSString *lineText = [oneObject valueForKey:kLineTextKey];

        UITextField *theField = self.lineFields[lineNum];
        theField.text = lineText;
    }
}

-(NSManagedObjectContext *)myContext{
    //上下文 关联Company.xcdatamodeld模型文件
    NSManagedObjectContext *context = [[NSManagedObjectContext alloc] init];
    //模型文件
    NSManagedObjectModel *model = [NSManagedObjectModel mergedModelFromBundles:nil];
    //持久化存储调度器
    NSPersistentStoreCoordinator *store = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:model];
    NSString *doc = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    NSString *sqlitePath = [doc stringByAppendingPathComponent:@"line.sqlite"];
    //数据存储的类型 数据库存储路径
    [store addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:[NSURL fileURLWithPath:sqlitePath] options:nil error:nil];
    context.persistentStoreCoordinator = store;
    
    return context;
}


- (IBAction)saveClicked:(id)sender {
    
    NSManagedObjectContext *context = [self myContext];
    
    NSError *error;
    for (int i = 0; i < 4; i++) {
        UITextField *theField = self.lineFields[i];
        NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:kLineEntityName];
        NSPredicate *pred = [NSPredicate predicateWithFormat:@"(%K = %d)", kLineNumberKey, i];
        [request setPredicate:pred];

        NSArray *objects = [context executeFetchRequest:request error:&error];
        if (objects == nil) {
            NSLog(@"There was an error!");
        }
        NSManagedObject *theLine = nil;
        if ([objects count] > 0) {
            theLine = [objects objectAtIndex:0];
        }else{
            theLine = [NSEntityDescription insertNewObjectForEntityForName:kLineEntityName inManagedObjectContext:context];
        }
        [theLine setValue:[NSNumber numberWithInt:i] forKey:kLineNumberKey];
        [theLine setValue:theField.text forKey:kLineTextKey];
    }
    [context save:nil];
    
}