Objective-C：NSArray的常见操作

NSArray不可变字符串的主要操作有：创建、枚举、排序、与NSString之间的相互转换

注意：

NSArray可以存对象，不可以存基本数据类型、结构体、数组、指针、nil、NULL

NSArray用nil作为结束标识符。

NSNull可以代表一个空对象。

整个操作还是通过代码来体现吧：

　　　　.h Person类的声明文件如下：　　

#import <Foundation/Foundation.h>

@interface Person : NSObject

@property(nonatomic,copy)NSString* name;

@property(nonatomic,assign)NSInteger age;

+(Person*)personWithName:(NSString*)name andAge:(NSInteger)age;

-(id)initWithName:(NSString*)name andAge:(NSInteger)age;

-(NSComparisonResult)compareByName:(Person *)aPerson;//声明排序方式为通过姓名比较

-(NSComparisonResult)compareByAge:(Person *)aPerson;//声明排序方式为通过年龄比较

@end

　　　　.m Person类的实现文件如下：

#import "Person.h"

@implementation Person

+(Person*)personWithName:(NSString*)name andAge:(NSInteger)age

{

return [[Person alloc]initWithName:name andAge:age];

}

-(id)initWithName:(NSString*)name andAge:(NSInteger)age

{

self = [super init];

if(self)

{

_name = name;

_age = age;

}

return self;

}

-(NSString*)description//由于数组存储的是自定义的对象Person对象,所以复写description方法，将NSlog重新格式化输出

{

return  [NSString stringWithFormat:@"name=%@,age=%ld",_name,_age];

}

-(NSComparisonResult)compareByName:(Person *)aPerson //返回一个selector选择器选择的比较方式,字符串比较默认为NSOrderAsecding

{

return [_name compare:aPerson.name];

}

-(NSComparisonResult)compareByAge:(Person *)aPerson//与上同理

{

if(_age > aPerson.age)

return NSOrderedDescending;

else if (_age < aPerson.age)

return NSOrderedAscending;

else

return NSOrderedSame;

}

@end

　　　　主函数测试如下：

#import <Foundation/Foundation.h>

#import "Person.h"

int main(int argc, const char * argv[])

{

@autoreleasepool

{

//NSArray测试

/*

NSArray可以存对象，不可以存基本数据类型、结构体、数组、指针、nil、NULL

NSArray用nil作为结束标识符。

NSNull可以代表一个空对象。

*/

//创建一个空对象

NSNull *nul = [NSNull null];

//在一个array中不要求只存相同类型的对象，可以存储任意类型的对象

NSArray *arr = @[@1,@"one",@"2",nul];

NSLog(@"%@",arr);

//枚举

NSEnumerator *enumerator = [arr objectEnumerator];

id obj;

while(obj = [enumerator nextObject])

{

NSLog(@"%@",obj);

}

//保存到文件中(必须是OC内置的对象,自定义的对象会出错)

[arr writeToFile:@"/Users/mac/Desktop/arr.txt" atomically:YES];

//读文件创建NSArray

NSArray *arr1 = [NSArray arrayWithContentsOfFile:@"/Users/mac/Desktop/arr.txt"];

NSLog(@"%@",arr1);

//排序

NSArray *arr2 =  @[@2,@5,@1,@4,@3];

NSArray *sorted = [arr2 sortedArrayUsingSelector:@selector(compare:)];

NSLog(@"%@",sorted);

NSArray *arr3 = @[@"two",@"three",@"five",@"one",@"four"];

NSArray *sorted2 = [arr3 sortedArrayUsingSelector:@selector(compare:)];

NSLog(@"%@",sorted2);

//自定义对象的排序

NSArray *arrayperson = @[[Person personWithName:@"Tom" andAge:25],

[Person personWithName:@"Jobs" andAge:23],

[Person personWithName:@"Bill" andAge:26],

[Person personWithName:@"John" andAge:21]];

//按姓名排序

NSArray *sortedByName = [arrayperson sortedArrayUsingSelector:@selector(compareByName:)];

NSLog(@"%@",sortedByName);

//按年龄排序

NSArray *sortedByAge = [arrayperson sortedArrayUsingSelector:@selector(compareByAge:)];

NSLog(@"%@",sortedByAge);

//NSArray和NSString

NSString *str = @"this is a test";

NSArray *words = [str componentsSeparatedByString:@" "];//分隔符

NSLog(@"%@",words);

NSString *str2 = [words componentsJoinedByString:@"-"]; //连接符

NSLog(@"%@",str2);

}

return 0;

}

　　　　　　测试结果如下所示：

-- ::39.772 -NSArray[:] (
    ,
    one,
    ,
    "<null>"
)
-- ::39.795 -NSArray[:]
-- ::39.796 -NSArray[:] one
-- ::39.797 -NSArray[:]
-- ::39.797 -NSArray[:] <null>
-- ::39.798 -NSArray[:] (null)
-- ::39.798 -NSArray[:] (
    ,
    ,
    ,
    ,

)
-- ::39.799 -NSArray[:] (
    five,
    four,
    one,
    three,
    two
)
-- ::39.799 -NSArray[:] (
    "name=Bill,age=26",
    "name=Jobs,age=23",
    "name=John,age=21",
    "name=Tom,age=25"
)
-- ::39.800 -NSArray[:] (
    "name=John,age=21",
    "name=Jobs,age=23",
    "name=Tom,age=25",
    "name=Bill,age=26"
)
-- ::39.800 -NSArray[:] (
    this,
    is,
    a,
    test
)
-- ::39.800 -NSArray[:] this-is-a-test
Program ended with exit code: