二、IOS SDK详解之NSArray/NSMutableArray

转载自:http://blog.csdn.net/hello_hwc/article/details/42714719

前言：本文会首先讲一下本人使用NSArray的几个小技巧，然后详解下常用的属性和方法。

一 NSArray/NSMutableArray简介

   NSArray存储的是一组对象的数组，这些对象是有序的，NSArray内容不可改变，如果需要可改变的使用NSMutableArray，它是NSArray的子类,在Cocoa touch中处于Core Service层。当然，也可以继承NSArray来自定义自己的数组，不过这种情况极少，这里不做讲解。通常如果需要Array的其他，创建类别（category足矣）

继承关系:NSArray->NSObject

遵循协议: NSCopying,NSFastEnumeration,NSObject,NSMutableCopying,NSSecureCoding

  NSMutableArray继承自NSArray。

继承关系:NSMutableArray->NSArray->NSObject

遵循协议：NSCopying,NSFastEnumeration,NSObject,NSMutableCopying,NSSecureCoding

二 使用NSArray的小技巧

2.1 快捷创建符号@[]

例如

 NSArray *array = @[@“1",@"2",@"3"];

2.2 firstObject:安全返回第一个元素

取NSArray有两种方式，用array[0]在数组为空的时候会报错，用[array firstObject]即使数组为空，也不会报错，会返回nil

同理lastObject也一样，

2.3 makeObjectsPerformSelector:withObject: 和makeObjectsPerformSelector:让每个数组内元素都执行某个SEL，这样写就不必再写个for语句了

2.4 KVC的方式取值，做计算

例如有个数组：

   NSArray * array = @[
                     @{@"name":@"hwc",
                       @"count":@(10),
                       @"url":@"blog.csdn.net/hello_hwc"
                       },
                     @{@"name":@"baidu",
                       @"count":@(20),
                       @"url":@"www.baidu.com"
                       },
                     @{@"name":@"google",
                       @"count":@(22),
                       @"url":@"www.google.com"
                       }
                     ];
 NSArray * nameArray = [array valueForKeyPath:@"name"];
 NSNumber *sum = [array valueForKeyPath:@"@sum.count"];
 NSNumber *max = [array valueForKeyPath:@"@max.count"];
 NSNumber *min = [array valueForKeyPath:@"@min.count"];
 NSLog(@"NameArray:%@",nameArray.description);
 NSLog(@"Sum:%@",sum.description);
 NSLog(@"max:%@",max.description);
 NSLog(@"min:%@",min.description);

输出

 HwcFoundationExample[1048:42991] NameArray:(
     hwc,
     baidu,
     google
 )
 2015-01-12 14:10:45.357 HwcFoundationExample[1048:42991] Sum:52
 2015-01-12 14:10:45.357 HwcFoundationExample[1048:42991] max:22
 2015-01-12 14:10:45.357 HwcFoundationExample[1048:42991] min:10

三 NSArray常用属性方法详解

为了更加直观，通过一个例子来展示，常用的使用属性和方法几乎都可以从例子中找到。

NSArray例子

 //初始化（Initializing an array）
     NSArray * array = [[NSArray alloc] initWithObjects:@"first",@"thrid",@"Second", nil nil];
     //查找(Querying an array)
     NSString * toFindString = @"Second";
     if ([array containsObject:toFindString]) {
         NSUInteger index = [array indexOfObject:toFindString];
         NSLog(@"%@ index is %lu",toFindString,index);
     }
     NSString * firstObject = [array firstObject];
     NSString * lastObject = [array lastObject];
     if (firstObject!=nil) {
         NSLog(@"First object is:%@",firstObject);
     }
     if (lastObject!=nil) {
         NSLog(@"LastObject object is:%@",lastObject);
     }
     //排序（Sort）
     NSArray * anotherArray = @[@"1",@"4",@"3"];
     NSArray * sortedArrayWithSEL = [array sortedArrayUsingSelector:@selector(localizedCompare:)];
     NSArray * sortedArrayWithComparator = [anotherArray sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
         NSString * str1 = obj1;
         NSString * str2 = obj2;
         if (str1.integerValue > str2.integerValue) {
             return NSOrderedDescending;
         }
         if (str1.integerValue < str2.integerValue) {
             return NSOrderedAscending;
         }
         return NSOrderedSame;
     }];

     if ([sortedArrayWithComparator isEqualToArray:sortedArrayWithSEL]) {
         NSLog(@"The array is same");
     }
     else{
         NSLog(@"The array is not same");
     }
     //与文件进行操作（Working with file）
     //如果存在则读到数组里，如果不存在则写到文件里（If exist read，else write to file）
     NSFileManager * defaultManager = [NSFileManager defaultManager];
     NSArray * paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
     NSString * documentDirectory = [paths firstObject];
     NSString * fileName = @"TestArray.plist";
     NSString * filePath = [documentDirectory stringByAppendingPathComponent:fileName];
     BOOL fileExist = [defaultManager fileExistsAtPath:filePath];
     if (fileExist) {
         //从文件读取
         NSArray * readArray = [NSArray arrayWithContentsOfFile:filePath];
         //遍历
         [readArray enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOLBOOL *stop) {
             if ([obj isKindOfClass:[NSString class]]) {
                 NSString * str = obj;
                 NSLog(@"At index:%lu is %@",idx,str);
                 if ([str isEqualToString:@"thrid"]) {
                     *stop = YES;
                 }
             }
         }];
     }else{
         [anotherArray writeToFile:filePath atomically:YES];
     }

NSMutableArray

 //(初始化)Init
 NSMutableArray* mutableArray = [[NSMutableArray alloc] initWithObjects:@"2",@"3",@"4", nil nil];
 //（添加对象）Add object
 [mutableArray addObject:@"5"];
 [mutableArray insertObject:@"1" atIndex:0];
 //(删除对象)Remove object
 [mutableArray removeObject:@"3"];
 [mutableArray removeObjectAtIndex:0];
 [mutableArray removeLastObject];

这段代码第一次运算输出

 2015-01-14 19:48:46.499 HwcNSArrayExample[509:7777] Second index is 2
 2015-01-14 19:48:46.501 HwcNSArrayExample[509:7777] First object is:first
 2015-01-14 19:48:46.501 HwcNSArrayExample[509:7777] LastObject object is:Second
 2015-01-14 19:48:46.502 HwcNSArrayExample[509:7777] The array is not same

第二次运算输出

 2015-01-14 19:49:31.135 HwcNSArrayExample[525:8151] Second index is 2
 2015-01-14 19:49:31.135 HwcNSArrayExample[525:8151] First object is:first
 2015-01-14 19:49:31.136 HwcNSArrayExample[525:8151] LastObject object is:Second
 2015-01-14 19:49:31.136 HwcNSArrayExample[525:8151] The array is not same
 2015-01-14 19:49:31.136 HwcNSArrayExample[525:8151] At index:0 is 1
 2015-01-14 19:49:31.137 HwcNSArrayExample[525:8151] At index:1 is 4
 2015-01-14 19:49:31.137 HwcNSArrayExample[525:8151] At index:2 is 3

注意，在使用writeToFile的时候，Array中的对象类型可以是

NSString，NSData，NSDate，NSNumber,NSArray,NSDictionary

不可以是其他类型的对象

至于完整的属性和方法，见官方文档，还是那句话，一定要能看懂官方文档。

转载自:http://blog.csdn.net/hello_hwc/article/details/42714719