构造方法的初认识

#import <Foundation/Foundation.h>
#import "Apple.h"

int main(int argc, const char * argv[]) {
    @autoreleasepool {
//        Apple *app = [[Apple alloc] init];
        Apple *apple = [Apple alloc];
        Apple *appleInit = [apple init];
        NSLog(@"%d",apple->_count);
        
        // 一个对象只有一个初始化方法，调用一次之后不能再次调用
         Apple *apple1 = [[Apple alloc] initWithCount:20];
         Apple *a = [apple1 initWithCount:200];
         Apple *b = [apple1 init];
         NSLog(@"%d",b->_count);
        
        Apple *apple2 = [[Apple alloc] initWithCount:100];
        NSLog(@"%d",apple2->_count);

    }
    return 0;
}

#import <Foundation/Foundation.h>

@interface Apple : NSObject
{
@public;
    int _count;
}
// id 万能指针可以指向任何类型
// 构造函数
// 1. 无参构造函数
- (instancetype)init;

// 2.有参的构造函数
- (instancetype)initWithCount:(int)count;
@end

#import "Apple.h"

@implementation Apple
- (instancetype)init
{
    // self 当前对象
    // super 当前类的父类
    // [super init] 初始化父类
    
    // 1. 加载父类资源
    if (self = [super init]) {
        // 初始化对象
        // 2.加载自己的资源
        _count = 10;
        
    }
    
    // 3. 资源加载完成返回
    return self;
}

- (instancetype)initWithCount:(int)count
{
    if (self = [super init]) {
        _count = count;
    }
    return self;
}
@end

构造函数

#import <Foundation/Foundation.h>
#import "Apple.h"
#import "Human.h"

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        // 获取苹果对象
        Apple *apple10 = [[Apple alloc] initWithCount:10];
        Apple *apple20 = [[Apple alloc] initWithCount:20];
        
        // 获取人对象
        Human *xiaoMing = [[Human alloc] initWithApple:apple10];
        Human *xiaoHuang = [[Human alloc] initWithApple:apple20];
        
        // 以后获取对象必须调用构造函数
        Human *xxx = [[Human alloc] init];
        
        // 计算结果
        int count = xiaoMing->_apple->_count + xiaoHuang->_apple->_count;
    }
    return 0;
}

#import "Apple.h"

@implementation Apple
- (instancetype)initWithCount:(int)count
{
    if (self = [super init]) {
        _count = count;
    }
    return self;
}
@end

#import <Foundation/Foundation.h>
#import "Apple.h"

@interface Human : NSObject
{
    @public;
    Apple *_apple;
}

- (instancetype)initWithApple:(Apple *)apple;
@end

#import "Human.h"

@implementation Human
- (instancetype)initWithApple:(Apple *)apple
{
    if (self = [super init]) {
        _apple = apple;
    }
    return self;
}
@end