1. 引言

在iOS開發(fā)調(diào)試過程中，打印日志是最常使用的手段，但是打印日志有時候無法提供詳細(xì)的信息用于問題的分析，?例如一般的消息數(shù)據(jù)由于數(shù)據(jù)量較大，打印日志時只會選擇將一些關(guān)鍵信息打印出來，信息不夠完整。因此，如果能將存入sqlite數(shù)據(jù)庫中的數(shù)據(jù)導(dǎo)出，對于問題的分析定位解決?將會十分有幫助。

2. python解析sqlite基本數(shù)據(jù)類型^[1]

2.1 數(shù)據(jù)庫基本操作

• 數(shù)據(jù)庫連接

import sqlite3
conn = sqlite3.connect('example.db')  

• 數(shù)據(jù)庫連接對象基本操作

cur = conn.cursor()    //創(chuàng)建cursor
conn.commit()          //事務(wù)提交
conn.rollback()        //事務(wù)回滾
conn.close()           //關(guān)閉一個數(shù)據(jù)庫鏈接

• 數(shù)據(jù)庫cursor基本操作

cur.execute()    //執(zhí)行sql語句
cur.fetchone()   //從結(jié)果中取出一條記錄
cur.fetchall()   //從結(jié)果中取出所有記錄
cur.close()      //關(guān)閉cursor

2.2 獲取數(shù)據(jù)庫中的表

sqlite數(shù)據(jù)庫中都包含一個特殊的表sqlite_master，其表結(jié)構(gòu)為：

CREATE TABLE sqlite_master (
type TEXT,
name TEXT,
tbl_name TEXT,
rootpage INTEGER,
sql TEXT);

可以利用此表來查詢數(shù)據(jù)庫中所有的表：

tables = cur.execute("select name from sqlite_master where type = 'table' order by name").fetchall()

2.3 獲取表結(jié)構(gòu)

columns = cur.execute("PRAGMA table_info(%s)" % table).fetchall()

2.4 獲取表中的數(shù)據(jù)

data = cur.execute("select * from %s" % table).fetchall()

3. iOS序列化存儲

在iOS開發(fā)中，經(jīng)常將可能會擴(kuò)展或者根據(jù)不同類型存儲不同數(shù)據(jù)的數(shù)據(jù)庫字段定義為blob類型，采用NSKeyedArchiver對具有差異性的數(shù)據(jù)進(jìn)行序列化，轉(zhuǎn)為NSData數(shù)據(jù)進(jìn)行存儲。

例如消息的數(shù)據(jù)表結(jié)構(gòu)可定義為：

CREATE TABLE ?message (
msgId integer primary key,
msgType int,
extensionData blob);

其中extensionData就可以根據(jù)消息的類型（?例如文本、圖片、多媒體等），存儲不同的數(shù)據(jù)；同時extensionData中的數(shù)據(jù)還可以在不改變表結(jié)構(gòu)的條件下，進(jìn)行其自身的數(shù)據(jù)擴(kuò)展。

?假設(shè)圖片消息類定義為：

@interface PicMsg : NSObject
@property (nonatomic, assign) NSUInteger msgType;
@property (nonatomic, strong) PicInfo *picInfo;
@end

其中PicInfo為圖片基本信息：

@interface PicInfo : NSObject<NSCoding>
@property (nonatomic, assign) ?NSUInteger picType;
@property (nonatomic, assign) ?NSUInteger fileSize;
@property (nonatomic, assign) ?NSUInteger picWidth;
@property (nonatomic, assign) ?NSUInteger picHeight;
@end

@implementation PicInfo
-(void)encodeWithCoder:(NSCoder *)coder
{
    [coder encodeObject:@(self.picType) forKey:@"picType"];
    [coder encodeObject:@(self.fileSize) forKey:@"fileSize"];
    [coder encodeObject:@(self.picWidth) forKey:@"picWidth"];
    [coder encodeObject:@(self.picHeight) forKey:@"picHeight"];
}
-(id)initWithCoder:(NSCoder *)decoder
{
    if (self = [super init]) {
        self.msgType = [[decoder decodeObjectForKey:@"picType"] unsignedIntegerValue];
        self.fileSize = [[decoder decodeObjectForKey:@"fileSize"] unsignedIntegerValue];
        self.picWidth = [[decoder decodeObjectForKey:@"picWidth"] unsignedIntegerValue];
        self.picHeight = [[decoder decodeObjectForKey:@"picHeight"] unsignedIntegerValue];
    }
    return self;
}
@end

這樣在存入數(shù)據(jù)庫時就可以調(diào)用[NSKeyedArchiver archivedDataWithRootObject:self.picFileInfo];，將picInfo轉(zhuǎn)化為NSData存入extensionData字段里。

4. python+pyobjc^[2]解析序列化數(shù)據(jù)

4.1 pyobjc

PyObjC is a bridge between Python and Objective-C. It allows full featured Cocoa applications to be written in pure Python. It is also easy to use other frameworks containing Objective-C class libraries from Python and to mix in Objective-C, C and C++ source.

在使用pyobjc和iOS相關(guān)框架時，只需要import相關(guān)模塊即可，例如Foundation框架：

from Foundation import *

4.2 pyobjc解析序列化數(shù)據(jù)

• 定義?對應(yīng)類

要對打包數(shù)據(jù)進(jìn)行解包，需要用python定義與OC相對應(yīng)的類。
例如第3節(jié)中提到的PicInfo，改用python定義為:

class PicInfo(NSObject):
    def init(self):
        self = super(PicInfo, self).init()
        if self is None:
            print "init None"
        return self
    def initWithCoder_(self, encoder):
        self = super(PicInfo, self).init()
        if self is None:
            print "initWithCoder_ None"
        self.picType = encoder.decodeObjectForKey_("picType")
        self.fileSize = encoder.decodeObjectForKey_("fileSize")
        self.picWidth = encoder.decodeObjectForKey_("picWidth")
        self.picHeight = encoder.decodeObjectForKey_("picHeight")
        return self
    def encodeWithCoder_(self, decoder):
        decoder.encodeObject_forKey_(self.picType, "picType")
        decoder.encodeObject_forKey_(self.fileSize, "fileSize")
        decoder.encodeObject_forKey_(self.picWidth, "picWidth")
        decoder.encodeObject_forKey_(self.picHeight, "picHeight")

• 數(shù)據(jù)的序列化與反序列化

picInfo = PicInfo.alloc().init()
picInfo.picType = 1
picInfo.fileSize = 1024
picInfo.picWidth = 200
picInfo.picHeight = 100
// 序列化
archivedData = NSKeyedArchiver.archivedDataWithRootObject_(picInfo)
// 反序列化
unarchivedPicInfo = NSKeyedUnarchiver.unarchiveObjectWithData_(archivedData)

5. 結(jié)語

python+pyobjc不僅僅可以在iOS開發(fā)時進(jìn)行數(shù)據(jù)的序列化和反序列化，利用pyobjc可以在Mac OS上使用純python開發(fā)Cocoa GUI應(yīng)用，功能非常強(qiáng)大。

參考資料

[1]sqlite3 DB-API 2.0 interface for SQLite databases
[2]pyobjc module
[3]pyobjc package documentation