iOS - 数组与字典(NSArray & NSDictionary)

概述

主要介绍数组与字典及使用示例。

数组

1.不可变数组

NSString *s1 = @"zhangsan";
NSString *s2 = @"lisi";
NSString *s3 = @"wangwu";
//(1)
NSArray *array1 = [[NSArray alloc] initWithObjects:s1,s2,s3, nil];
NSLog(@"%@",array1); //等价于 array1.descripton
        
//(2)使用类方法创建
        
NSArray *array2 = [NSArray arrayWithObjects:s1,s2,s3, nil];
//(3)创建一个数组对象，同时往里面存入一元素
NSArray *array3 = [NSArray arrayWithObject:s1];
        
//(4)创建一个数组，此数组中的元素来自array1
NSArray *array4 = [NSArray arrayWithArray:array1];
NSLog(@"array4 = %@",array4);

• 通过下标取元素

NSString *str1 = [array4 objectAtIndex:0];

• 数组元素的个数

NSUInteger count = [array4 count];  //等价于：array4.count;

• 判断数组中的是否包含某个元素

BOOL isContains = [array4 containsObject:@"zhangsan"];
NSLog(@"isContains:%d",isContains);

• 查找某一个对象在数组中的下标位置

NSUInteger index = [array4 indexOfObject:@"wangwu"];
if (index == NSNotFound) {
    NSLog(@"Not find elemnts");
} else {
    NSLog(@"index = %ld",index);
}

• 链接数组中的字符串(前提：数组中都是字符串）

NSString *joinString = [array4 componentsJoinedByString:@","];
NSLog(@"joinString = %@",joinString);

• 访问数组最后一个元素

NSString *lastObj = [array4 lastObject];  //array4.lastObject
NSLog(@"lsatObj = %@",lastObj);

• 在原来的数组后面添加一个元素

NSArray *array5 = [array4 arrayByAddingObject:@"zhaolia"];
NSLog(@"array5 = %@",array5);
//取对应下标元素
        int idx=4;
        if (idx <array5.count) {
            NSString *s = [array5 objectAtIndex:idx];
            NSLog(@"s = %@",s);
        }
        
        //--------------数组的遍历
        //1.普通遍历
        for (int i=0; i<array5.count; i++) {
            NSString *str = [array5 objectAtIndex:i];
            NSLog(@"%@",str);
        }
        
        //快速遍历
        for (NSString *s in array5) {
            NSLog(@"%@",s);
        }
        
        //4.4之后的优化
//1.创建一个素组
NSArray *array7 = @[s1,s2,s3]; //等价于：NSArray *array7 = [NSArray arrayWithObjects:s1,s2,s3,nil];
NSLog(@"array7 = %@",array7);
        
NSString *str = array7[0];
NSLog(@"array[7] = %@",str);

2.可变数组

 //初始化，设定元素个数为5，可以更改的。（继承自NSArray）
        NSMutableArray *mutableArray = [NSMutableArray arrayWithCapacity:5];
        
        //想数组中添加一个元素
        [mutableArray addObject:@"aaa"];
        //向数组中指定下标插入元素
        [mutableArray insertObject:@"ccc" atIndex:0];
        NSLog(@"%@",mutableArray);   //原来位置元素后移
        
        //移除最后一个元素
        [mutableArray removeLastObject];
        NSLog(@"移除最后元素后：%@",mutableArray);
        
        //移除指定元素
        [mutableArray removeObject:@"aaa"];
        
        //移除指定下标元素
        [mutableArray removeObjectAtIndex:0];
        
        //向数组中添加数组
        [mutableArray addObjectsFromArray:array1];

• 创建可变数组

   NSString *t1 = @"zhangsan ";
        NSString *t2 = @"lisi";
        NSString *t3 = @"wangwu ";
        
//        NSMutableArray *mArray1 = @[s1,s2,s3];//wrong.这里创建了一个不可变数组
        NSMutableArray *mArray1 = [[NSMutableArray alloc] initWithObjects:s1,s2,s3, nil];
        
        //创建数组时，开辟3个空间用于存储元素，存储超过容量，数组自动增大空间
        NSMutableArray *mArray2 = [[NSMutableArray alloc] initWithCapacity:3];
        
        NSMutableArray *mArray3 = [NSMutableArray arrayWithCapacity:3];

• 添加元素

 [mArray2 addObject:t1];
        [mArray2 addObject:t2];
        [mArray2 addObject:t3];
        NSLog(@"mArray2= %@",mArray2);
        
        //将mArray2 中元素添加到mArray3中
//        [mArray3 addObjectsFromArray:mArray2];
        
        //将mArray2作为二维数字添加
        [mArray3 addObject:mArray2];
        NSLog(@"mArray3 = %@",mArray3);

• 插入元素

[mArray2 insertObject:@"Jack" atIndex:0];
        NSLog(@"mArray2 = %@",mArray2);

• 替换元素

[mArray2 replaceObjectAtIndex:0 withObject:@"John"];
        NSLog(@"替换：%@",mArray2);

• 互换两个元素的位置

[mArray2 exchangeObjectAtIndex:3 withObjectAtIndex:0];
        NSLog(@"mArray2 = %@",mArray2);

• 删除元素

//6.1根据下标删除
        [mArray2 removeObjectAtIndex:2];
        NSLog(@"mArray2 = %@",mArray2);
        
        //6.2删除最后一个元素
        [mArray2 removeLastObject];
        NSLog(@"mArray2 = %@",mArray2);
        
        //6.3删除指定的对象
        //[mArray2 removeObject:@"zhangsan"];
        
        //6.4删除所有元素
        [mArray2 removeAllObjects];
        NSLog(@"mArray2 = %@",mArray2);

字典

1.不可变字典

• 字典的创建

NSArray *array1 = [NSArray arrayWithObjects:@"zhangsan",@"zhangfei",nil];
        NSArray *array2 = [NSArray arrayWithObjects:@"lisi",@"liping", nil];
        
        //第一元素：key：@“zhang"   value:array1
        //第二元素：key: @"li:      value:array2
        NSDictionary *dic1 = [[NSDictionary alloc] initWithObjectsAndKeys:array1,@"zhang",array2,@"li", nil];
        
        NSUInteger count = dic1.count; //字典元素个数
        NSLog(@"count:%d",count);
        
        //创建字典时初始化一个元素
        NSDictionary *dic2 = [NSDictionary dictionaryWithObject:array1 forKey:@"zhang"];
        NSLog(@"dic2 = %@",dic2);

• 获取字典中所有的key

NSArray *allKeys = [dic1 allKeys]; //dic1.allKeys.
        NSLog(@"allKeys= %@",allKeys);
        //3.获取字典中所有的value
        NSArray *allValues = [dic1 allValues];
        NSLog(@"allValues = %@",allValues);

• 通过key取得value

NSArray *array3 = [dic1 objectForKey:@"zhang"];
        NSLog(@"array3 = %@",array3);
        
        //------------字典中优化的方法
        NSDictionary *dic3 = @{@"zhang": array1,@"li":array2};
        NSLog(@"dic3 = %@",dic3);
        
        //取value的语法：字典［”key“］
        NSArray *array4 = dic3[@"zhang"]; //等价于：NSArray *array3 = [dic3 objectForKey:@"zhang"];
        NSLog(@"array4 = %@",array4);

2.可变字典

• 创建一个可变字典

NSMutableDictionary *md1 = [[NSMutableDictionary alloc] initWithCapacity:3];

• 添加元素

 [md1 setObject:array1 forKey:@"zhang"];
        [md1 setObject:array2 forKey:@"li"];
        NSLog(@"md1 = %@",md1);
        
        
        //将字典dic1 中所有的元素添加到md1字典中
        [md1 addEntriesFromDictionary:dic1];
        NSLog(@"md1 = %@",md1);
        
//        [md1 setObject:@"zhangsan" forKey:@"zhang"]; //如果添加相同的key,会将原来的Value覆盖掉

• 删除（根据key删除元素）

[md1 removeObjectForKey:@"zhang"];
        NSLog(@"md1 = %@",md1);
        //删除所有元素（清空）
        //[md1 removeObjects];
        
//        //根据多个key删除对应的多个元素
//        [md1 removeObjectsForKeys:@[@"zhang",@"li"]];
//        NSLog(@"md1 = %@",md1);

• 遍历字典

//1.快速遍历
        for (NSString *key in md1) {
            NSArray *name = [md1 objectForKey:key];
            NSLog(@"快速遍历：key = %@,value = %@",key,name);
        }
        
        //2.普通遍历
        NSArray *allKeys2 = [md1 allKeys];
        for (int i = 0; i<allKeys.count - 1; i++) {
            NSString *key = allKeys2[i];
            NSArray *name = md1[key];
            NSLog(@"普通遍历：key = %@,value = %@",key,name);
        }