Objective-C笔记系列（1）— — Foundation

1.NSArray数组

NSArray是一个有序的静态数组，子类NSMutableArray创建的是动态数组。可以用下标取值。

创建方法

字面值创建,NSArray字面值创建不可以存nil，如类方法arrayWithObjects接收到nil时判定列表结束

//由编译器产生底层创建代码，调用arrayWithObjects:count:方法。
NSArray *array = @[someObject, @"Hello, World!", @42];

等同于

id objects[] = { someObject, @"Hello, World!", @42 };
NSUInteger count = sizeof(objects) / sizeof(id);
NSArray *array = [NSArray arrayWithObjects:objects
                                     count:count];

常用类方法

+ array  //用于子类NSMutableArray创建
+ (instancetype)arrayWithArray:(NSArray<ObjectType> *)array;
+ (instancetype)arrayWithObjects:(ObjectType)firstObj, ...;

常用实例变量方法

- (NSUInteger) count;  //获取数组大小
- (ObjectType)objectAtIndex:(NSUInteger)index;  //返回索引处对象
- (BOOL)containsObject:(ObjectType)anObject;   //查找是否有该对象
- (NSEnumerator<ObjectType> *)objectEnumerator; //枚举器方法

枚举与快速枚举

//枚举器
NSEnumerator *em = [array objectEnumerator];
while (id inde = [em nextObject]){
    do someting with inde;
}
//快速枚举
for (NSString * st in array)
{
    do something with st;
}  

更多内容参考NSArray

2.NSDictionary字典

同样地，NSDictionary是静态不可变的词典，而其子类NSMutableDictionary可变

创建方法

字面值创建

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

等同于

id objects[] = { someObject, @"Hello, World!", @42, someValue };
id keys[] = { @"anObject", @"helloString", @"magicNumber", @"aValue" };
NSUInteger count = sizeof(objects) / sizeof(id);
NSDictionary *dictionary = [NSDictionary dictionaryWithObjects:objects
                                                       forKeys:keys
                                                         count:count];

常用类方法

+ (instancetype)dictionaryWithObjects:(NSArray<ObjectType> *)objects 
                              forKeys:(NSArray<id<NSCopying>> *)keys;

常用实例变量方法

- (ObjectType)objectForKey:(KeyType)aKey;
- (void)setObject:(ObjectType)anObject 
           forKey:(id<NSCopying>)aKey;      //for NSMutableDictionary
- (void)removeObjectForKey:(KeyType)aKey;   //for NSMutableDictionary

更多见

NSDictionary

NSMutableDictionary

3.NSSet

NSSet的内容是无序的，其主要作用是查看某一特定对象是否存在。

常用类方法

+ (instancetype)setWithObjects:(ObjectType)firstObj, ...;
+ (instancetype)setWithArray:(NSArray<ObjectType> *)array;

常用实例变量用法

- (BOOL)containsObject:(ObjectType)anObject;
- (void)addObject:(ObjectType)object;    //for NSMutableSet
- (void)removeObject:(ObjectType)object; //for NSMutableSet

更多见

NSSet

NSMutableSet