IOS本地持久化有4种：属性列表、对象归档、SQLite3和Core Data；
其中属性列表和SQlite3是本人强烈推荐的。对象归档较为繁琐，coreData没有用过暂不评价。
1.属性列表简单说一下：最普遍用的最广泛的持久化方法；
- 1).分开存取
// 存
[[NSUserDefaults standardUserDefaults] setInteger:userID forKey:@”userID”];
[[NSUserDefaults standardUserDefaults] setObject:name forKey:@”name”];
// 取
NSInteger uId = [[[NSUserDefaults standardUserDefaults] integerValueForKey:@”userID”];
NSString * name = [[NSUserDefaults standardUserDefaults] stringForKey:@”name”]; - 2).按对象存取
// 存
[[NSUserDefaults standardUserDefaults] setObject:self forKey:@”user”];
// 取
User * u = [[NSUserDefaults standardUserDefaults] [objectForKey”@”user]；
2.好了进入今天的正题~数据库Sqlite3
说到SQlite3嵌入式数据库不得不提一个强大的第三方FMDB
有FMDB,OC与SQlite的交互变得不那么困难,化繁为简。但是很多小伙伴对sqlite语法很陌生，导致FMDB无缘无故的坑自己。
下面我就来简单分享自己对FMDB的理解以及IOS数据库本地持久化的万能常用语句。-
最开始我们建一个单例类来创建和管理数据库。
如下：
@implementation DataBaseManagerShoppingCar
{
//数据库管理对象
FMDatabase *_fmdb;
}
-(instancetype)init{
//1.抛异常
@throw [NSException exceptionWithName:@"DataBaseManagerShoppingCar" reason:@"不能调用初始化方法" userInfo:nil];
return self;
//2.断言，判定言论，程序崩溃
// NSAssert(false, @"DataBaseManager无法调用该方 法");
}
//重新实现初始化方法
-(instancetype)initWithPrivate
{
if (self =[super init]) {
[self createDataBase];
}
return self;
}+(instancetype)sharedManager { static DataBaseManagerShoppingCar *manager =nil; static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ if (!manager) { manager =[[DataBaseManagerShoppingCar alloc]initWithPrivate]; } }); return manager; // //2. // @synchronized(self){ // if (!manager) { // manager =[[self alloc]initPrivate]; // } // } } //初始化数据库 -(void)createDataBase { //获取沙箱路径下的Documents NSArray *documentsPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *dbPath =[[documentsPath fir stObject]stringByAppendingPathComponent:@"ShoppingCar.db"]; NSLog(@"%@",dbPath); if (!_fmdb) { //创建数据库管理对象 _fmdb =[[FMDatabase alloc]initWithPath:dbPath]; } //打开数据库 if ([_fmdb open]) { //创建数据库表 [_fmdb executeUpdate:@"create table if not exists ShoppingCar (productId integer, productName str, thumb str,type integer,num integer,unitPrice double,farmId integer,deliveryWeekIndex integer,payType integer);"]; } }
增删查
判断APPID对应的数据是否存在
-(BOOL)isExistsProductId:(NSInteger)productId
{
FMResultSet * rs =[_fmdb executeQuery:@"select *from ShoppingCar where productId =?",@(productId)];
// 判断结果集是否存在
// if ([rs next]) {
// return YES;
// }
// else{
// return NO;
// }
return [rs next];
}-
添加数据
-(BOOL)insertProductId:(NSInteger)productId ProductName:(NSString )productName Thumb:(NSString *)thumb Type:(NSInteger)type Num:(NSInteger)num UnitPrice:(double)unitPrice FarmId:(NSInteger)farmId DeliveryWeekIndex:(NSInteger)deliveryWeekIndex PayType:(NSInteger)payType
{
//判断AppId在数据库中是否存在
//这里要特别提出来说一下，问号代表的是对象，如果你存的常量请先转成对象存进去。比如@(Float) 还有
if(![self isExistsProductId:productId]){
//如果不存在
BOOL success =[_fmdb executeUpdate:@"insert into ShoppingCar values(?,?,?,?,?,?,?,?,?)",@(productId),productName,thumb,@(type),@(num),@(unitPrice),@(farmId),@(deliveryWeekIndex),@(payType)];
return success;
}
return YES;
}
-(BOOL)removeAllobjects
{
BOOL succese = [_fmdb executeUpdate:@"delete from ShoppingCar"];
return succese;
}
-(BOOL)removeProductId:(NSInteger)productId
{
BOOL succese =[_fmdb executeUpdate:@"delete from ShoppingCar where productId=?",@(productId)];
return succese;
}
-(managerModel *)selectCurrentModelWithProductId: (NSInteger)productId
{
FMResultSet *rs =[_fmdb executeQuery:@"select *from ShoppingCar where productId =?",@(productId)];
managerModel *model =[[managerModel alloc]init];
while([rs next]){
model.productId =[rs intForColumn:@"productId"];
model.productName =[rs stringForColumn:@"productName"];
model.thumb =[rs stringForColumn:@"thumb"];
model.type =[rs intForColumn:@"type"];
model.num =[rs intForColumn:@"num"];
model.unitPrice =[rs doubleForColumn:@"unitPrice"];
model.farmId =[rs intForColumn:@"farmId"];
model.deliveryWeekIndex =[rs intForColumn:@"deliveryWeekIndex"];
model.payType =[rs intForColumn:@"payType"];
}
return model;
}-(NSArray *)selectAllApps { //从表中获取所有数据 FMResultSet *rs =[_fmdb executeQuery:@"select *from ShoppingCar"]; //遍历结果集 NSMutableArray *apps =[NSMutableArray array]; while([rs next]){ managerModel *model =[[managerModel alloc]init]; model.productId =[rs intForColumn:@"productId"]; model.productName =[rs stringForColumn:@"productName"]; model.thumb =[rs stringForColumn:@"thumb"]; model.type =[rs intForColumn:@"type"]; model.num =[rs intForColumn:@"num"]; model.unitPrice =[rs doubleForColumn:@"unitPrice"]; model.farmId =[rs intForColumn:@"farmId"]; model.deliveryWeekIndex =[rs intForColumn:@"deliveryWeekIndex"]; model.payType =[rs intForColumn:@"payType"]; [apps addObject:model]; } return [apps copy]; } //修改数据 -(BOOL)updateProductId:(NSInteger)productId Num: (NSInteger)num { BOOL succese =[_fmdb executeUpdate:@" update ShoppingCar set num =? where productId=?",@(num),@(productId)]; return succese; } FMDB的三种查询方法
-(FMResultSet )executeQuery:(NSString)sql, ...
- (FMResultSet )executeQueryWithFormat:(NSString)format, ...
- (FMResultSet *)executeQuery:(NSString *)sql withArgumentsInArray:(NSArray *)arguments
// executeUpdate : 不确定的参数用?来占位
[self.db executeUpdate:@"INSERT INTO t_student (name, age) VALUES (?, ?);", name, @(arc4random_uniform(40))];
//也可以这样表示
//NSString *tableName =@"t_student (name, age)";
//[self.db executeUpdate:[NSString stringWithFormat:@"insert into %@ VALUES(?,?)" ,tableName],name, @(arc4random_uniform(40))];
[self.db executeUpdate:@"INSERT INTO t_student (name, age) VALUES (?, ?);" withArgumentsInArray:@[name, @(arc4random_uniform(40))]];
// executeUpdateWithFormat : 不确定的参数用%@、%d等来占位
//此处一定要注意Format后面不是单纯的字符串NSString，不能随便的组装字符串，它只能接Values括号里面的占位参数，不能更改Values前面的参数，例如：
错误的表达:
[self.db executeUpdateWithFormat:@"INSERT INTO %@ VALUES (%@, %d);", @"t_student (name, age)"，name, arc4random_uniform(40)];
正确表达:
[self.db executeUpdateWithFormat:@"INSERT INTO t_student (name, age) VALUES (%@, %d);", name, arc4random_uniform(40)];
