Archiving and recovery of data using Nskeyedarchiver in iOS

1, relevant knowledge points:

<1> types of objects that can be archived and recovered using Nskeyedarchiver: NSString, Nsdictionary, Nsarray, NSData, NSNumber, etc.

<2> use is the Nscoding protocol object that must be followed to implement two methods:

Encodewithcoder: This method is called when an object is archived.

Initwithcoder: This method is called every time an object is recovered from a file.

2. A simple example illustrates the detailed steps

<1> Create a student-to-like hustudent, follow the nscoding protocol, and give the student a set of three attributes:

@property (nonatomic, copy) NSString *name;

@property (nonatomic, assign) double height;

@property (nonatomic, assign) int age;

<2> using the first method for storing data: Need to describe the properties that need to be stored

-(void) Encodewithcoder: (Nscoder *) encoder

{

[Encoder encodeObject:self.name forkey:@ "name"];

[Encoder encodeInt:self.age forkey:@ "age"];

[Encoder encodeDouble:self.height forkey:@ "height"];

}

<3> parse an object using the second method: Read Object properties

-(ID) Initwithcoder: (Nscoder *) decoder

{

if (self = [super init])

{

Self.name = [Decoder decoderobjectforkey:@ "name"];

Self.age = [Decoder decoderobjctforkey:@ "age"];

Self.height = [Decoder decoderobjectforkey:@ "height"];

}

return self;

}

<4> Assigning and reading model objects in the controller

>> property Assignment for model objects

//----1. the new Model object

Hustudent * student = [[Hustudent alloc]init];

Student.name = @ "Hulin";

Student.age = 24;

Student.height = 1.83;

-----2. Archiving Model objects

NSString * doc = [Nssearchpathfordirectoriesindomains (Nsdocumentdirectory,nsuserdomainmask,yes) Lastobject]; Get documents Full path

NSString * Path = [doc stringbyappendingpathcomponent:@ "Student.plist"]; Get the full path of a file

Nsarray * array = @[student];

[Nskeyedarchiver Archiverootobject:array Tofile:path]; Archive an Object

-----3. Read the properties of a model object

NSString * Doc =[nssearchpathfordirectoriesindomains (Nsdocumentdirectory,nsuserdomainmask,yes) lastObject]; Get documents Full path

NSString * Path = [doc stringbyappendingpathcomponent:@ "Student.plist"]; Get the full path of the file

Hustudent * student = [Nskeyedunarchiver Unarchiveobjectwithfile:path]; Reading an object from a file

NSLog (@ "%@,%d,%f", student.name,student.age,student.height);

3, the use of nskeyedarchiver storage data considerations:

If the subclass and parent class created in the program follow the Nscoding protocol, add [self encodewithcode:encode] to the Encodewithcoder: method (to ensure that the inherited instance variable can also be encoded); Initwithcoder: plus self = [super Initwithcoder:decoder] (ensure instance variables can also be decoded);