关于数组内元素是否会被改变的思考

- (void)pmy_updateCachedArr:(NSArray<HTBNWaitBusesM4Cal *> *)cachedArr     withNewInfoArr:(NSArray<HTBNWaitBusesM4Cal *> *)newInfoArr{
    [newInfoArr enumerateObjectsUsingBlock:^(HTBNWaitBusesM4Cal * _Nonnull obj,NSUInteger idx,BOOL * _Nonnull stop) {
        for (int i = 0; i < cachedArr.count; ++i) {
            HTBNWaitBusesM4Cal *lM = cachedArr[i];
            if ([lM isEqual:obj]) {
                
                //不能这么做，lM地址会变，但是无法影响for循环外面数组中元素的地址！！！思考作用域原理即可理解。
//                lM = obj;

//外面数组中元素的属性是可以被改变的
                lM.gNearestStaM = obj.gNearestStaM;
            }
        }
    }];
}

• 不同的循环语法不影响结果
• 数组是否可变不影响结果
• 想改变数组中模型的地址，必须用系统方法！模型的属性可以被改变
• 想想变量赋值原理和作用域的概念，可能会豁然开朗

#import "ViewController.h"
#import "Person.h"
@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    [self test1];
    [self test2];
    [self test3];
    //[self test4];
    //[self test5];
}

- (void)test1{
    Person *lP1 = [[Person alloc] init];
    lP1.gStr4Name = @"1号";
    
    Person *lP2 = [[Person alloc] init];
    lP2.gStr4Name = @"2号";
    
    lP1 = lP2;
    NSLog(@"%@,%@",lP1,lP2);
    NSLog(@"test1 lP1.gStr4Name:%@",lP1.gStr4Name);
}

- (void)test2{
    Person *lP1 = [[Person alloc] init];
    lP1.gStr4Name = @"1号";
    
    Person *lP2 = [[Person alloc] init];
    lP2.gStr4Name = @"2号";
    
    NSArray *lArr1 = @[lP1];
    NSArray *lArr2 = @[lP2];
    [lArr1 enumerateObjectsUsingBlock:^(Person *  _Nonnull obj,BOOL * _Nonnull stop) {
        for (int i = 0; i < lArr2.count; ++i) {
            Person *lP2 = lArr2.lastObject;
            obj = lP2;
        }
    }];
    
    Person *lP = lArr1.firstObject;
    NSLog(@"%@,lP2);
    
    //原以为会打印 2号，想想变量赋值原理和作用域的概念，豁然开朗
    NSLog(@"test2 lP.gStr4Name:%@",lP.gStr4Name);
}

- (void)test3{
    Person *lP1 = [[Person alloc] init];
    lP1.gStr4Name = @"1号";
     NSLog(@"1  P1:%@",lP1);
    Person *lP2 = [[Person alloc] init];
    lP2.gStr4Name = @"2号";
     NSLog(@"1  P2:%@",lP2);
    
    NSArray *lArr1 = @[lP1];
    NSArray *lArr2 = @[lP2];
    
    //不同的循环语法不影响结果
    for (int i = 0; i < lArr1.count; ++i) {
        Person *lP1 = lArr1.firstObject;
         NSLog(@"2  P1:%@",lP1);
        for (int j = 0; j < lArr2.count; ++j) {
            Person *lP2 = lArr2.lastObject;
            lP1 = lP2;
            NSLog(@"2 P2:%@",lP2);
        }
         NSLog(@"3  P1:%@",lP1);
    }
    
    Person *lP = lArr1.firstObject;
    NSLog(@"4:%@,lP2);
    NSLog(@"test3 lP.gStr4Name:%@",lP.gStr4Name);
}

- (void)test4{
    Person *lP1 = [[Person alloc] init];
    lP1.gStr4Name = @"1号";
     NSLog(@"1  P1:%@",lP2);
    
    //数组是否可变不影响结果
    NSMutableArray *lArr1 = [NSMutableArray arrayWithArray:@[lP1]];
    NSMutableArray *lArr2 = [NSMutableArray arrayWithArray:@[lP2]];
    for (int i = 0; i < lArr1.count; ++i) {
        Person *lP1 = lArr1.firstObject;
         NSLog(@"2  P1:%@",lP.gStr4Name);
}

- (void)test5{
    Person *lP1 = [[Person alloc] init];
    lP1.gStr4Name = @"1号";
     NSLog(@"1  P1:%@",lP2);
    
    NSMutableArray *lArr1 = [NSMutableArray arrayWithArray:@[lP1]];
    NSMutableArray *lArr2 = [NSMutableArray arrayWithArray:@[lP2]];
    for (int i = 0; i < lArr1.count; ++i) {
        Person *lP1 = lArr1.firstObject;
         NSLog(@"2  P1:%@",lP1);
        for (int j = 0; j < lArr2.count; ++j) {
            Person *lP2 = lArr2.lastObject;
            
            //想改变数组内容，必须用系统方法！
            [lArr1 replaceObjectAtIndex:0 withObject:lP2];
        }
         NSLog(@"3  P1:%@",lP.gStr4Name);
}


@end