Objective C 总结（七）：Foundation Kit中的常类型

Objective-C是C的超集，C中的类型和操作在Objective-C中都是可用的。

Foundation 框架提供了一些常用的struct。struct是值类型

1. NSRance

   typedef struct _NSRange 
   {
       unsigned int location;
       unsigned int length;
   } NSRange;

   第一种初始化方法

   NSRange range;
   range.location = 11;
   range.length = 55;

   第二种方法

   NSRange range = {17, 55};

   第三种方法，使用框架提供的C函数，这种编程方式在objective-c开发中大量的使用了

   NSRange range = NSMakeRange(11, 55);

2. NSPoint

   typedef struct _NSPoint
   {
       float x;
       float y;
   } NSPoint;

3. NSSize

   typedef struct _NSSize 
   {
       float width;
       float height;
   } NSSize;

4. NSRect

   typedef struct _NSRect
   {
       NSPoint origin;
       NSSize size;
   } NSRect;

   上面的结构都提供了快捷C函数,NSMakePoint(x,y),NSMakeSize(width,height),NSMakeRect(x,y,width,height)

字符串

NSString-不可变字符串和NSMutableString可变字符串，框架中大量的类提供的不可变版本和可变版本。如NSArray和NSMutableArray,NSDictionary和NSMutableDictionary,NSSet和NSMutableSet.

1. 创建
   

   NSString *name = @"Bob";
   NSString *name = [[NSString alloc] initWithFormat: @"My name is %@", @"Bob"];
   NSString *name = [NSString stringWithFormat: @"My name is %@", @"Bob"];
   NSString *name = [NSString stringWithUTF8String: "My name is Bob“];

2. 比较
   比较内容的相等用

   - (BOOL) isEqualToString: (NSString *) aString;

   注意下面这样比较的是对象

   if(aString == bString)

   - (NSComparisonResult) compare: (NSString *)string;
   - (NSComparisonResult) compare: (NSString *)string
                                    options: (unsigned int) mask;

   typedef enum _NSComparisonResult
   {
       NSOrderedAscending = -1,
       NSOrderedSame,
       NSOrderedDescending
   } NSComparisonResult;

   NSMutableString提供了追加、删除、替换等的方法。
   

   - (void) appendString: (NSString *) aString;
   - (void) appendFormat: (NSString *) format;
   - (void) deleteCharactersInRange: (NSRange) range;

集合

集合中只能存储引用对象，如要存储基本类型需要用NSNumber将它们先装箱。集合中不能存储nil,初始化时以nil结束。

1. NSArray， 顺序集合，它分配一块连续的内存区域
   初始化方法，
   

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

   NSArray *someArray =
     [NSArray arrayWithObjects: firstObject, secondObject, thirdObject, nil];

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

   查询

       NSUInteger numberOfItems = [someArray count]; 
       if ([someArray containsObject:someString]) {
           ...
       }
       // 访问对象
       if ([someArray count] > 0) {
           NSLog(@"First item is: %@", [someArray objectAtIndex:0]);
       }
       // 用下标方式访问对象
       if ([someArray count] > 0) {
           NSLog(@"First item is: %@", someArray[0]);
       }

   排序

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

   可变数组

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

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

2. NSSet 非顺序集合，存储不重复对象的集合，用法与NSArray一样
3. NSDictionary 字典，以key-value对的方式存储的数据结构
   创建

      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
       };

   查询

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

   可变字典

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

   NSNull可作为空值存储到集合中，它只有一种用法[NSNull null]，表示空对象，nil则表示空地址

      NSArray *array = @[ @"string", @42, [NSNull null] ];
       for (id object in array) {
           if (object == [NSNull null]) {
               NSLog(@"Found a null object");
           }
       }

快速枚举器：for()，用于遍历集合，但不能修改集合中对象的值，用法

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

各种数值包装类

1. NSNumber，对基本类型的对象形式装箱（即作为对象存储到heap中），拆箱即获取原来的值
   

       NSNumber *magicNumber = [[NSNumber alloc] initWithInt:42];
       NSNumber *unsignedNumber = [[NSNumber alloc] initWithUnsignedInt:42u];
       NSNumber *longNumber = [[NSNumber alloc] initWithLong:42l];
    
       NSNumber *boolNumber = [[NSNumber alloc] initWithBOOL:YES];
    
       NSNumber *simpleFloat = [NSNumber numberWithFloat:3.14f];
       NSNumber *betterDouble = [NSNumber numberWithDouble:3.1415926535];
    
       NSNumber *someChar = [NSNumber numberWithChar:'T'];

   上面实例方法都提供了对应的类方法，下面是快速语法

       NSNumber *magicNumber = @42;
       NSNumber *unsignedNumber = @42u;
       NSNumber *longNumber = @42l;
    
       NSNumber *boolNumber = @YES;
    
       NSNumber *simpleFloat = @3.14f;
       NSNumber *betterDouble = @3.1415926535;
    
       NSNumber *someChar = @'T';

   拆箱

    int scalarMagic = [magicNumber intValue];
       unsigned int scalarUnsigned = [unsignedNumber unsignedIntValue];
       long scalarLong = [longNumber longValue];
    
       BOOL scalarBool = [boolNumber boolValue];
    
       float scalarSimpleFloat = [simpleFloat floatValue];
       double scalarBetterDouble = [betterDouble doubleValue];
    
       char scalarChar = [someChar charValue];

   NSNumber是不可变的。

2. NSValue 对结构类型的装箱
   

   NSRect rect = NSMakeRect(1,2,30,40);
   
   NSValue *value = [NSValue valueWithBytes: &rect
                                        objCType: @encode(NSRect)];

   拆箱

   [value getValue: &rect];

   对于常见的结构框架已封闭好了方法

   + NSValue *)valueWithPoint: (NSPoint) point;
   + (NSValue *) valueWithSize: (NSSize) size;
   
   - (NSPoint) pointValue;
   - (NSSize) sizeValue;