IOS SDK详解之NSArray/NSMutableArray

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blog.csdn.net/hello_hwc

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:522015-01-12 14:10:45.357 HwcFoundationExample[1048:42991] max:222015-01-12 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];    //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, BOOL *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];    //（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 22015-01-14 19:48:46.501 HwcNSArrayExample[509:7777] First object is:first2015-01-14 19:48:46.501 HwcNSArrayExample[509:7777] LastObject object is:Second2015-01-14 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 22015-01-14 19:49:31.135 HwcNSArrayExample[525:8151] First object is:first2015-01-14 19:49:31.136 HwcNSArrayExample[525:8151] LastObject object is:Second2015-01-14 19:49:31.136 HwcNSArrayExample[525:8151] The array is not same2015-01-14 19:49:31.136 HwcNSArrayExample[525:8151] At index:0 is 12015-01-14 19:49:31.137 HwcNSArrayExample[525:8151] At index:1 is 42015-01-14 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。