NSArray功能扩展

获取数组中的对象

/// 获取数组中的对象
/// @param index 为正值 左->右 , 负值   左<-右
- (id)exp_objAtIndex:(NSInteger)index;

例子 ：

   NSArray *arry = @[@"1",@"2",@"3"];
 
    //左->右
    NSString * str0 =  [arry exp_objAtIndex:0];
    NSString * str1 =  [arry exp_objAtIndex:1];
    NSString * str2 = [arry exp_objAtIndex:2];
    NSLog(@"====%@===%@====%@",str0,str1,str2);
    
    //左<-右
    NSString * str_1 =  [arry exp_objAtIndex:-1];
    NSString * str_2 = [arry exp_objAtIndex:-2];
    NSString * str_3 =  [arry exp_objAtIndex:-3];
    NSLog(@"====%@===%@====%@",str_1,str_2,str_3);

运行结果 ：

数组是否为空

/// 数组是否为空
- (BOOL)isEmpty;

例子 ：

    NSArray *arry = @[@"1",@"2",@"3"];
    if (arry.isEmpty) {
        NSLog(@"空");
    }else{
        NSLog(@"有值");
    }

运行结果 ：

数组映射

/// 映射
/// @param mapper 映射规则
- (NSArray *)mapper:(id(^)(id obj))mapper;

例子 ：

    NSArray *arry = @[@"1",@"2",@"3"];
   NSArray *mapperArray = [arry mapper:^id _Nonnull(NSString * obj) {
        return [obj stringByAppendingString:@"_1"];
    }];
    NSLog(@"======%@",mapperArray);

运行结果 ：

数组筛选

/// 筛选
/// @param filter 筛选规则
- (NSArray *)filter:(BOOL(^)(id obj))filter;

例子 ：

  NSArray *arry = @[@"1",@"2",@"3"];
    NSArray *filterArray = [arry filter:^BOOL(NSString * obj) {
        return  [obj isEqualToString:@"2"];
    }];
    NSLog(@"======%@",filterArray);

运行结果 ：

数组元素拼接

/// 数组元素拼接
 -(NSString *(^)(NSString *separator))joinedByString;

例子 ：

   NSArray *arry = @[@"1",@"2",@"3"];
  NSString *str =   arry.joinedByString(@",");
    NSLog(@"======%@",str);

运行结果 ：

源码

.h

//
//  NSArray+Expand.h
//  数组的扩展
//
//  Created by 崔志伟 on 2020/10/13.
//  Copyright © 2020 崔志伟. All rights reserved.
//

#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface NSArray (Expand)

/// 获取数组中的对象
/// @param index 为正值 左->右 , 负值   左<-右
- (id)exp_objAtIndex:(NSInteger)index;
 
/// 数组是否为空
- (BOOL)isEmpty;

/// 映射
/// @param mapper 映射规则
- (NSArray *)mapper:(id(^)(id obj))mapper;

/// 筛选
/// @param filter 筛选规则
- (NSArray *)filter:(BOOL(^)(id obj))filter;

/// 数组元素拼接
 -(NSString *(^)(NSString *separator))joinedByString;


@end

NS_ASSUME_NONNULL_END

.m

//
//  NSArray+Expand.m
//  数组的扩展
//
//  Created by 崔志伟 on 2020/10/13.
//  Copyright © 2020 崔志伟. All rights reserved.
//

#import "NSArray+Expand.h"

@implementation NSArray (Expand)

- (id)exp_objAtIndex:(NSInteger)index{
   
    if (index >=0) {
        return [self objectAtIndex:index];
    }else{
        return [self objectAtIndex:self.count +index];
    }
}

- (BOOL)isEmpty{
    return self.count<=0;
}

- (NSArray*)mapper:(id(^)(id obj))mapper{
    NSMutableArray *array = [NSMutableArray array];
    for (id item in self) {
        if (mapper) {
            id newItem =  mapper(item);
            [array addObject:newItem];
        }
    }
    return array.copy;
}

- (NSArray*)filter:(BOOL(^)(id obj))filter{
    NSMutableArray *array = [NSMutableArray array];
    for (id item in self) {
        if (filter) {
            BOOL isFit =  filter(item);
            if (isFit) {
                [array addObject:item];
            }
        }
    }
    return array.copy;
}


-(NSString *(^)(NSString *separator))joinedByString{
    return  ^(NSString *separator) {
        return  [self componentsJoinedByString:separator];
    };
}
@end