工作在Fundation框架下2——Start Developing iOS Apps Today——从今天开始开发IOS（IOS7版）系列源文档翻译（十六）

+ (id)arrayWithObject:(id)anObject;
+ (id)arrayWithObjects:(id)firstObject, ...;
- (id)initWithObjects:(id)firstObject, ...;

NSArray *someArray =
[NSArray arrayWithObjects:someObject, someString, someNumber, someValue, nil];

id firstObject = @"someString";
id secondObject = nil;
id thirdObject = @"anotherString";
NSArray *someArray =
  [NSArray arrayWithObjects:firstObject, secondObject, thirdObject, nil];

NSArray *someArray = @[firstObject, secondObject, thirdObject];

id firstObject = @"someString";
id secondObject = nil;
NSArray *someArray = @[firstObject, secondObject];
// exception: "attempt to insert nil object"

遍历数组对象

NSUInteger numberOfItems = [someArray count];
 
if ([someArray containsObject:someString]) {
    ...
}

if ([someArray count] > 0) {
    NSLog(@"First item is: %@", [someArray objectAtIndex:0]);
}

if ([someArray count] > 0) {
    NSLog(@"First item is: %@", someArray[0]);
}

排序数组对象

NSArray *unsortedStrings = @[@"gammaString", @"alphaString", @"betaString"];
NSArray *sortedStrings =
         [unsortedStrings sortedArrayUsingSelector:@selector(compare:)];

不确定性

NSMutableString *mutableString = [NSMutableString stringWithString:@"Hello"];
NSArray *immutableArray = @[mutableString];

if ([immutableArray count] > 0) {
    id string = immutableArray[0];
    if ([string isKindOfClass:[NSMutableString class]]) {
        [string appendString:@" World!"];
    }
}

NSMutableArray *mutableArray = [NSMutableArray array];
[mutableArray addObject:@"gamma"];
[mutableArray addObject:@"alpha"];
[mutableArray addObject:@"beta"];
 
[mutableArray replaceObjectAtIndex:0 withObject:@"epsilon"];

[mutableArray sortUsingSelector:@selector(caseInsensitiveCompare:)];

集合

NSSet *simpleSet =
  [NSSet setWithObjects:@"Hello, World!", @42, aValue, anObject, nil];

  NSNumber *number = @42;
    NSSet *numberSet =
      [NSSet setWithObjects:number, number, number, number, nil];

字典

NSDictionary *dictionary = [NSDictionary dictionaryWithObjectsAndKeys:
               someObject, @"anObject",
         @"Hello, World!", @"helloString",
                      @42, @"magicNumber",
                someValue, @"aValue",
                      nil];

NSDictionary *dictionary = @{
              @"anObject" : someObject,
           @"helloString" : @"Hello, World!",
           @"magicNumber" : @42,
                @"aValue" : someValue
};

NSNumber *storedNumber = [dictionary objectForKey:@"magicNumber"];

NSNumber *storedNumber = dictionary[@"magicNumber"];

不确定性

[dictionary setObject:@"another string" forKey:@"secondString"];
[dictionary removeObjectForKey:@"anObject"];

NSArray *array = @[ @"string", @42, [NSNull null] ];

for (id object in array) {
    if (object == [NSNull null]) {
        NSLog(@"Found a null object");
    }
}