OC - NSArray 和 NSNumber

1.数组的创建

NSArray *array1 =[[NSArray alloc]initWithObjects:@"iphone",@"ipad",@"iWatch", nil];
NSArray *array2= [NSArray arrayWithObjects:@"A",@"B",@"C", nil];
NSArray *array3 =@[@"beijin",@"guangzhou",@"shanghai"];(字面量方法创建)

2.通过下标取值

1. array3[1]
2. [array3 objectAtIndex:2]
注意：下标是从0开始

3.添加元素

NSArray  *array4 =[array3 arrayByAddingObject:@"shenzhen"];

4.数组转换为字符串

NSString *str =[array4 componentsJoinedByString:@","];

5.将字符串转化为数组

NSString *str1 =@"ios Andriod WP";
NSArray  *array5 =[str1 componentsSeparatedByString:@" "];

6.通过对象去查找下标

NSInteger index=[array4 indexOfObject:@"shanghai"];

6.通过对象去查找下标

NSInteger index=[array4 indexOfObject:@"shanghai"];

7.数组的便利

for (int i=0; i<[array4 count]; i++){
      id a=[array4 objectAtIndex:i];//因为不知道a是啥类型  所以用id
 }

8.快速便利

for (id b in array4)//不知道啥类型的b，对array4便利
{
     NSLog(@"b=%@",b);
}

9.可变数组

NSMutableArray *mArray =[[NSMutableArray alloc]initWithObjects:@"a",@"b",@"c",@"d", nil];

9.1可变数组追加

[mArray addObject:@"e"];

9.2可变数组插入

[mArray insertObject:@"f" atIndex:2];

9.3可变数组删除

[mArray removeObjectAtIndex:3];

9.4可变数组替换

[mArray replaceObjectAtIndex:2 withObject:@"F"];

10.NSNumber

float  a=3.2;
NSNumber *aNum =[[NSNumber alloc]initWithFloat:a];
NSLog(@"aNum=3.2");

10.1NSNumber将对象类型转化为基本类型

float b=[aNum floatValue];
NSLog(@"b=%.1f",b);b=3.2

NSString *_str=[NSString stringWithFormat:@"123.56"];
int c=[_str  intValue];
NSLog(@"c=%d",c);c=123