IOS data persistence 2 (archiving and anti-archiving)

Data Persistence is actually to store data on the network or hard disk, which is stored on the local hard disk. The local hard disk of the application is a sandbox, and the sandbox is actually a folder, it contains four folders. These are the documents, library, app package, and TMP folders. The documents mainly store files that users have been using for a long time. The library contains the caches and preferences folders, caches stores temporary files and caches them. Preferences stores preferences. TMP is a temporary file, but it is different from caches. Some files are compiled in the app package and cannot be modified.

First, create a person class and define three attributes.

. H file

# Import
<Foundation/Foundation. h>

@ Interface person:
Nsobject <nscoding>

{

Nsstring * Name;

Int age;

Nsstring * phone;

}

@ Property (nonatomic, retain) nsstring
* Name, * phone;

@ Property (nonatomic, assign) int age;

-(ID) initwithname :( nsstring *) aname phone :( nsstring *) aphone age :( INT) Aage; // Initialization Method

@ End

. M file

# Import
"Person. H"

@ Implementation person

@ Synthesize name, age, phone;

-(ID) initwithname :( nsstring *) aname phone :( nsstring *) aphone age :( INT) Aage

{

[Super
Init];

If (Self ){

Self. Name = aname;

Self. Phone = aphone;

Self. Age = Aage;

}

Return self;

}

-(Void) encodewithcoder :( nscoder *) acder // encode the attribute

{

[ACO
Encodeobject: Self. Name
Forkey: @ "name"];

[ACO
Encodeobject: Self. Phone
Forkey: @ "phone"];

[ACO
Encodeinteger: Self. Age
Forkey: @ "Age"];

}

-(ID) initwithcoder :( nscoder *) adecoder // decodes attributes

{

Nsstring * name1 = [adecoder decodeobjectforkey: @ "name"];

Nsstring * phone1 = [adecoder decodeobjectforkey: @ "phone"];

Int age1 = [adecoder decodeintegerforkey: @ "Age"];

[Self
Initwithname: name1
Phone: phone1 age: age1];

Return self;

}

@ End

Archive and archive in the main program

-(Void) loadview

{

Self. view = [[uiview alloc] initwithframe: cgrectmake (0, 0,320,460)];

Self. View. backgroundcolor = [uicolor whitecolor];

Person * P1 = [[person alloc] initwithname: @ "Jim" Phone: @ "654789" Age: 3];

Person * P2 = [[person alloc] initwithname: @ "Tom" Phone: @ "5464" Age: 4];

// File archiving

Nsmutabledata * Data = [nsmutabledata data];

// Create an archive class

Nskeyedarchiver * archiver = [[nskeyedarchiver alloc] initforwritingwithmutabledata: Data];

[Archiver encodeobject: P1 forkey: @ "person1"];

[Archiver encodeobject: P2 forkey: @ "person2"];

[Archiver finishencoding];

[Archiver release];

// Write data to a file

[Data writetofile: [self filepath] atomically: Yes];

// Archive and retrieve data from the file

Nsmutabledata * data1 = [nsmutabledata datawithcontentsoffile: [self filepath];

Nskeyedunarchiver * unarchiver = [[nskeyedunarchiver alloc] initforreadingwithdata: data1];

Person * P3 = [unarchiver decodeobjectforkey: @ "person1"];

Person * P4 = [unarchiver decodeobjectforkey: @ "person2"];

Nslog (@ "% @ % d", p3.name, p3.phone, p3.age );

Nslog (@ "% @ % d", p4.name, p4.phone, p4.age );

}

-(Nsstring *) filepath

{

Nsstring * docpath = [nssearchpathfordirectoriesindomains (nsdocumentdirectory, nsuserdirectory, yes) objectatindex: 0];

Nsstring * Path = [docpath stringbyappendingpathcomponent: @ "texts"];

// Nsstring * Path = [nshomedirectory () stringbyappendingpathcomponent: @ "Library/caches/texts"]; // either of the two methods can be used

Return path;

}