思路：既然我们需要改变NSArry和NSDictionary的系统类方法，所以我们可以利用运行时runtime来进行方法交换、另一种方法就是通过添加分类来重写类方法的实现。注意：这里不是添加类扩展。

为NSArry和NSDictionary添加分类

Object-C file.png

category.png

分类中的实现：
方式一：
删除.h文件（因为在项目里打印字典或数组时，使用的是系统的方法并不需要导入分类的头文件），.m文件下的实现，

#import <Foundation/Foundation.h>

@implementation NSDictionary (Log)

//重写系统的方法控制输出
-(NSString *)descriptionWithLocale:(id)locale indent:(NSUInteger)level
{
    NSMutableString *string = [NSMutableString string];
    
    //{}
    [string appendString:@"{"];
    
    //拼接key--value
    [self enumerateKeysAndObjectsUsingBlock:^(id  _Nonnull key, id  _Nonnull obj, BOOL * _Nonnull stop) {
        [string appendFormat:@"%@:",key];
        [string appendFormat:@"%@,",obj];
        
    }];
    [string appendString:@"}"];
    
    //删除逗号
    //从后往前搜索 得到的是搜索到的第一个符号的位置
    NSRange range = [string rangeOfString:@"," options:NSBackwardsSearch];
    if (range.location != NSNotFound) {
        [string deleteCharactersInRange:range];
    }
    
    return string;
}

@end

@implementation NSArray (Log)

//重写系统的方法控制输出
-(NSString *)descriptionWithLocale:(id)locale indent:(NSUInteger)level
{
    //    return @"你大爷是你大姐";
    NSMutableString *string = [NSMutableString string];
    
    //{}
    [string appendString:@"["];
    
    //拼接obj
    [self enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        [string appendFormat:@"%@,\n",obj];
    }];

    [string appendString:@"]"];
    
    //删除逗号
    //从后往前搜索 得到的是搜索到的第一个符号的位置
    NSRange range = [string rangeOfString:@"," options:NSBackwardsSearch];
    if (range.location != NSNotFound) {
        [string deleteCharactersInRange:range];
    }

    return string;
}

@end

方式二：
.h文件

#import <Foundation/Foundation.h>

@interface NSArray (desc)

@end


@interface NSDictionary (desc)

@end

.m文件

#import "NSArray+desc.h"

@implementation NSArray (desc)

- (NSString *)descriptionWithLocale:(id)locale
{
    NSMutableString *strM = [NSMutableString stringWithString:@"(\n"];
    
    [self enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
        [strM appendFormat:@"\t%@,\n", obj];
    }];
    
    [strM appendString:@")"];
    
    return strM;
}

@end

@implementation NSDictionary (desc)

- (NSString *)descriptionWithLocale:(id)locale
{
    NSMutableString *strM = [NSMutableString stringWithString:@"{\n"];
    
    [self enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
        [strM appendFormat:@"\t%@ = %@;\n", key, obj];
    }];
    
    [strM appendString:@"}\n"];
    
    return strM;
}

@end