LHF Objective-C语法（11）写入和读取属性 对象的复制

1、

NSArray *array = [[NSArray arrayWithObjects:@"Apple",@"Google",@"Microsoft",nil];

[array writeToFile:@"plist.txt" atomically:NO];

会在当前文件夹下找到plist.txt，格式如下

(

      Apple,

      Google,

      Microsoft

)

NSArray *array2 = [NSArray arrayWithContentOfFile:@"plist.txt"];

NSLog(@"%@",[array2 objectAtIndex:1]);

2、如果持久化的类型不是数组，字典，缓冲区，那该怎么办。

objc里也有java一样的序列化，反序列化  使用NSCoding协议

    -(void) encodeWithCoder :(NSCoder*) coder; //编码对象

    -(id) initWithCoder :(NSCoder*) decoder; //解码

@interface Person : NSObject <NSCoding>
{
    int pid;
    NSString *name;
    float height;
}

-(void) setPid:(int) pid;
-(void) setName:(NSString *) name;
-(void) setHeight:(float) height;

-(int) pid;
-(NSString *) name;
-(float) height;

@end

#import "Person.h"

@implementation Person

-(void) setPid:(int) p
{
    pid = p;
}
-(void) setName:(NSString *) n
{
    [n retain];
    [name release];
    name = n;
}
-(void) setHeight:(float) h
{
    height = h;
}

-(int) pid
{
    return pid;
}
-(NSString *) name
{
    return name;
}
-(float) height
{
    return height;
}

-(void) encodeWithCoder:(NSCoder *)aCoder
{
    [aCoder encodeObject:name forKey:@"name"];
    [aCoder encodeInt:pid forKey:@"pid"];
    [aCoder encodeFloat:height forKey:@"height"];
}

- (id)initWithCoder:(NSCoder *)coder {
    self = [super init];
    if (self) {
        name = [coder decodeObjectForKey:@"name"];
        [self setName:[coder decodeObjectForKey:@"name"]];
        pid = [coder decodeIntForKey:@"pid"];
        height = [coder decodeFloatForKey:@"height"];
    }
    return self;
}

- (void)dealloc {
    [name release];
    [super dealloc];
}

@end

int main (int argc, const char * argv[])
{

    @autoreleasepool {
        
        Person *p = [[Person alloc] init];
        [p setName:@"@Tom"];
        [p setPid:1];
        [p setHeight:188];
        
        NSData *data = [NSKeyedArchiver archivedDataWithRootObject:p];
        [data writeToFile:@"person.db" atomically:YES];
        [p release];
        
        Person *p2 = [NSKeyedUnarchiver unarchiveObjectWithData:data];
        NSLog(@"%@",[p2 name]);

3、对象的复制

某个对象是否可以被复制，要看它的类型是否遵从NSCopying协议，这个协议有个复制方法需要我们去实现

//Engine.h=======================================
#import <Foundation/Foundation.h>
@interface Engine:NSObject <NSCopying>//遵从NSCopying协议
@end
//Engine.m=======================================
@implementation Engine
-(id) copyWithZone:(NSZone*) zone{
  Engine *engine = [[[self class] allocWithZone:zone] init];
  return engine;
}
@end
//=======================================
@interface Tire:NSObject <NSCopying>{
  int count;
}
-(Tire*) initWithCount:(int) count;
-(void) setCount:(int) count;
-(int) count;
@end
//=======================================
@implementation Tire
-(Tire*) initWithCount:(int) c{
  self = [super init];
  if(self){count=c;}
  return self;
}
-(void) setCount:(int) c{
  count = c;
}
-(int) count{
  return count;
}
-(id) copyWithZone:(NSZone*) zone{
  Tire *tire = [[[self class] allocWithZone:zone] initWithCount:count];
  return tire;
}
@end
//========================================
@interface Car : NSObject <NSCopying>{
  Engine *engine;Tire *tire;
}
-(void) setEngine:(Engine*) engine;
-(void) setTire:(Tire*) tire;
-(Engine*) engine;
-(Tire*) tire;
@end
//========================================
@implementation Car
-(void) setEngine:(Engine*) e{
  [e retain];
  [engine release];
  engine = e;
}
-(void) setTire:(Tire*) t{
  [t retain];
  [tire release];
  tire = t;
}
-(Engine*) engine{
  return engine;
}
-(Tire*) tire{
  return tire;
}
-(id) copyWithZone:(NSZone*) zone{
  Car *car = [[[self class] allocWithZone:zone] init];
  Engine *engineCopy = [engine copy];
  Tire *tireCopy = [tire copy];
  [car setEngine:engineCopy];
  [car setTire:tireCopy];
  [engineCopy release];
  [tireCopy release];
  return car;
}
-(void) dealloc{
  [engine release];
  [tire release];
  [super dealloc];
}
@end
int main (int argc, const char * argv[]){    
  @autoreleasepool {                
    Engine *engine = [Engine new];        
    Tire *tire = [[Tire alloc] initWithCount:4];        
    Car *car = [Car new];        
    [car setEngine:engine];        
    [car setTire:tire];        
    [engine release];        
    [tire release];                
    Car *newCar = [car copy];        
    [car release];                
    NSLog(@"The car has %d tires",[[newCar tire] count]);        
    newCar release];            
  }    
  return 0;
}