iOS中Sqlite轻量级数据库的使用

Problem：

iOS的MVC模型中，将模型数据持久存储到iOS文件系统，通常有四种机制：属性列表、对象归档、iOS嵌入式关系数据库(SQLite3)、Apple提供的Core Data。属性列表和对象归档适合存取数据量不是很大的数据，在需要保存的数据比较多的时候，往往考虑使用数据库。SQLite3为iOS内嵌的一个轻量级的数据库，它提供了C实现的接口。为了更方便使用，你自己写一个封装了这些接口的类，如DBHelper，然后在其中定义自己的表、数据查询、插入、删除等等的接口。对于新手，那么该如何了解和开始使用SQLite3呢？这里或许能给你一些有意义的信息。

Solution：

(1) 了解SQLite，最好不过的就是去它的官方网站看详细的文档，这将是一个不错的起点。
http://www.sqlite.org/lang.html和http://www.sqlite.org/cintro.html
如果你认真把上面的文档读完了的话，那么相信你会对SQLite有了不错的理解，特别是了解了它所提供的接口。那么，你现在或许需要回忆一下以前所学过的数据库知识了，比如建表、查询、插入、删除等等的命令，当然这些命令在iOS的Sqlite使用中会略有差别。

(2) 《iOS 5基础教程》的数据持久化的那一章。

这本书不是一本很好的开发入门书籍，但是不能否认其中某些章节的内容还是不错的。如果是一个新手，一上来看这本书，或许会比较痛苦，它不太适合作为入门读得第一本书。但是如果能耐着心看上一两遍，其实发现这本书其实也还可以。而数据持久化的那一章，就有SQLite的简要介绍，可以提供一些例子给你参考。

看了这两个资料，相信你基本具备了编写代码使用SQLite数据库的能力了。

Example：

下面是自己摸索、实践并应用于项目中的代码示例。对照例子，或许能给你学习SQLite的使用带来更多的灵感。

//interface文件

//  Created by fengtao.ft on 14-5-13.

#import <Foundation/Foundation.h>

@interface TestDBHelper : NSObject

+ (TestDBHelper *)sharedInstance;

- (BOOL)insertNewRecord:(NSString *)imgURL
userId:(NSString *)userId
email:(NSString *)email
date:(NSString *)date;

- (BOOL)deleteRecordWithUserId:(NSString *)userId
email:(NSString *)email
date:(NSString *)date;

- (BOOL)deleteRecordWithUserId:(NSString *)userId;
- (BOOL)deleteAllRecords;
- (NSArray *)queryAllRecords;
- (NSArray *)quereRecordWithUserId:(NSString *)userId;

@end

//implementation文件

//  Created by fengtao.ft on 14-5-13.

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

#define kTestDBName @"TestDB.sqlite"
#define kImgUrl @"imgURL"
#define kUserId @"userId"
#define kEmail @"email"
#define kDate @"date"

@interface TestDBHelper ()
{
sqlite3 *testDB;
dispatch_queue_t testDBQueue;
}

@end

@implementation TestDBHelper

static TestDBHelper *sharedManager;
+ (TestDBHelper *) sharedInstance{

if (nil == sharedManager){
sharedManager = [[TestDBHelper alloc] init];
}
return sharedManager;
}

- (NSString *)databasePath{

NSString *dbFolderPath = [NSSearchPathForDirectoriesInDomains(NSDocumentationDirectory, NSUserDomainMask, YES) objectAtIndex:0];
dbFolderPath = [dbFolderPath stringByAppendingPathComponent:@"DBFolder"];
NSFileManager *manager = [NSFileManager defaultManager];
BOOL isDir;
if (![manager fileExistsAtPath:dbFolderPath isDirectory:&isDir]){
[manager createDirectoryAtPath:dbFolderPath
withIntermediateDirectories:YES
attributes:nil
error:nil];
}
dbFolderPath = [dbFolderPath stringByAppendingPathComponent:kTestDBName];

return dbFolderPath;
}

- (id)init{

if (self = [super init]){
testDBQueue = dispatch_queue_create("TestDBQueue", NULL);
[self createDatabaseIfNotExist];
}
return self;
}

- (void)createDatabaseIfNotExist{

//dispatch_async(testDBQueue, ^{

NSString *dbPath = [self databasePath];
int isOpen;
isOpen = sqlite3_open([dbPath UTF8String], &testDB);
if (isOpen != SQLITE_OK){
NSLog(@"Fail to open database");
sqlite3_close(testDB);
}else{
const char *createSQL = "CREATE TABLE IF NOT EXISTS testInfoTable \
(imgURL TEXT, userId TEXT, email TEXT, date TEXT)";
char *errMsg;
int isCreate = sqlite3_exec(testDB, createSQL, NULL, NULL, &errMsg);
if (isCreate != SQLITE_OK){
NSLog(@"Fail to create table");
}
sqlite3_close(testDB);
}
//});

}

- (BOOL)insertNewRecord:(NSString *)imgURL userId:(NSString *)userId email:(NSString *)email date:(NSString *)date{

BOOL isInsert = NO;

NSString *dbPath = [self databasePath];
if (sqlite3_open([dbPath UTF8String], &testDB) != SQLITE_OK){
sqlite3_close(testDB);
}else{
const char *insertSQL = "INSERT INTO testInfoTable (imgURL, userId, email, date) VALUES (?,?,?,?)";
sqlite3_stmt *insertStmt;
if(sqlite3_prepare_v2(testDB, insertSQL, -1, &insertStmt, NULL) == SQLITE_OK){
sqlite3_bind_text(insertStmt, 1, [imgURL UTF8String], -1, NULL);
sqlite3_bind_text(insertStmt, 2, [userId UTF8String], -1, NULL);
sqlite3_bind_text(insertStmt, 3, [email UTF8String], -1, NULL);
sqlite3_bind_text(insertStmt, 4, [date UTF8String], -1, NULL);
if(sqlite3_step(insertStmt) == SQLITE_DONE){
NSLog(@"Insert success");
isInsert = YES;
}
}
sqlite3_finalize(insertStmt);
sqlite3_close(testDB);
}

return isInsert;

}

- (BOOL)deleteRecordWithUserId:(NSString *)userId email:(NSString *)email date:(NSString *)date{

BOOL isDelete = NO;

NSString *dbPath = [self databasePath];
if(sqlite3_open([dbPath UTF8String], &testDB) != SQLITE_OK){
sqlite3_close(testDB);
}else{
const char *deleteSQL = "DELETE FROM testInfoTable WHERE userId = ? AND email = ? AND date = ?";
sqlite3_stmt *deleteStmt;
if(sqlite3_prepare_v2(testDB, deleteSQL, -1, &deleteStmt, NULL) == SQLITE_OK){
sqlite3_bind_text(deleteStmt, 1, [userId UTF8String], -1, NULL);
sqlite3_bind_text(deleteStmt, 2, [email UTF8String], -1, NULL);
sqlite3_bind_text(deleteStmt, 3, [date UTF8String], -1, NULL);
if(sqlite3_step(deleteStmt) == SQLITE_DONE){
NSLog(@"Delete sucess");
isDelete = YES;
}
}
sqlite3_finalize(deleteStmt);
sqlite3_close(testDB);
}

return isDelete;
}

- (BOOL)deleteRecordWithUserId:(NSString *)userId{

BOOL isDelete = NO;

NSString *dbPath = [self databasePath];
if(sqlite3_open([dbPath UTF8String], &testDB) != SQLITE_OK){
sqlite3_close(testDB);
}else{
const char *deleteSQL = "DELETE FROM TestInfoTable WHERE userId = ?";
sqlite3_stmt *deleteStmt;
int isPrepare = sqlite3_prepare_v2(testDB, deleteSQL, -1, &deleteStmt, NULL);
if( isPrepare == SQLITE_OK){
sqlite3_bind_text(deleteStmt, 1, [userId UTF8String], -1, NULL);
if(sqlite3_step(deleteStmt) == SQLITE_DONE){
NSLog(@"Delete success");
isDelete = YES;
}
}
sqlite3_finalize(deleteStmt);
sqlite3_close(testDB);
}

return isDelete;

}

- (BOOL)deleteAllRecords{

BOOL isDelete = NO;
NSString *dbPath = [self databasePath];
if(sqlite3_open([dbPath UTF8String], &testDB) != SQLITE_OK){
sqlite3_close(testDB);
}else{
const char *deleteSQL = "DELETE FROM TestInfoTable";
sqlite3_stmt *deleteStmt;
if(sqlite3_prepare_v2(testDB, deleteSQL, -1, &deleteStmt, NULL) == SQLITE_OK){
if(sqlite3_step(deleteStmt) == SQLITE_DONE){
NSLog(@"Delete all success");
isDelete = YES;
}
}
sqlite3_finalize(deleteStmt);
sqlite3_close(testDB);

}

return isDelete;
}

- (NSArray *)queryAllRecords{

NSString *dbPath = [self databasePath];
NSMutableArray *dataList = nil;
if(sqlite3_open([dbPath UTF8String], &testDB) != SQLITE_OK){
sqlite3_close(testDB);
}else{
const char *querySQL = "SELECT * FROM TestInfoTable";
sqlite3_stmt *queryStmt;
if(sqlite3_prepare_v2(testDB, querySQL, -1, &queryStmt, NULL) == SQLITE_OK){
dataList = [NSMutableArray array];
while(sqlite3_step(queryStmt) == SQLITE_ROW){
const char *imgurlChar = (const char *)sqlite3_column_text(queryStmt, 0);
const char *useridChar = (const char *)sqlite3_column_text(queryStmt, 1);
const char *emailChar = (const char *)sqlite3_column_text(queryStmt, 2);
const char *dateChar = (const char *)sqlite3_column_text(queryStmt, 3);

NSMutableDictionary *data = [NSMutableDictionary dictionaryWithCapacity:4];
[data setObject:[NSString stringWithUTF8String:imgurlChar] forKey:kImgUrl];
[data setObject:[NSString stringWithUTF8String:useridChar] forKey:kUserId];
[data setObject:[NSString stringWithUTF8String:emailChar] forKey:kEmail];
[data setObject:[NSString stringWithUTF8String:dateChar] forKey:kDate];

[dataList addObject:data];
}
}
sqlite3_finalize(queryStmt);
sqlite3_close(testDB);
}

return dataList;
}

- (NSArray *)quereRecordWithUserId:(NSString *)userId{

NSString *dbPath = [self databasePath];
NSMutableArray *dataList = nil;

if(sqlite3_open([dbPath UTF8String], &testDB) != SQLITE_OK){
sqlite3_close(testDB);
}else{
const char *querySQL = "SELECT * FROM TestInfoTable WHERE userId = ?";
sqlite3_stmt *queryStmt;
if(sqlite3_prepare_v2(testDB, querySQL, -1, &queryStmt, NULL) == SQLITE_OK){
dataList = [NSMutableArray array];
sqlite3_bind_text(queryStmt, 1, [userId UTF8String], -1, NULL);
while(sqlite3_step(queryStmt) == SQLITE_ROW){
const char *imgurlChar = (const char *)sqlite3_column_text(queryStmt, 0);
const char *useridChar = (const char *)sqlite3_column_text(queryStmt, 1);
const char *emailChar = (const char *)sqlite3_column_text(queryStmt, 2);
const char *dateChar = (const char *)sqlite3_column_text(queryStmt, 3);

NSMutableDictionary *data = [NSMutableDictionary dictionaryWithCapacity:4];
[data setObject:[NSString stringWithUTF8String:imgurlChar] forKey:kImgUrl];
[data setObject:[NSString stringWithUTF8String:useridChar] forKey:kUserId];
[data setObject:[NSString stringWithUTF8String:emailChar] forKey:kEmail];
[data setObject:[NSString stringWithUTF8String:dateChar] forKey:kDate];

[dataList addObject:data];
}
}
sqlite3_finalize(queryStmt);
sqlite3_close(testDB);
}

return dataList;
}

@end

Discussion:
（一些需要注意的东西，待总结补上）

Open Source Demo：

(provide git link coming soon......)