Foundation 学习笔记

笔记内容

学习笔记-段玉磊 Stanford course

Foundation and Attributed Strings

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Dynamic binding

• id 是一个指向任何未知对象的指针，(the consept of dynamic binding)
• 静态类型化：id 不会发生警告 而NSString *s 会发生警告！
• Nerver use iD ,因为id只是指针，很危险！！
• 强制转换需要保护！

id保护机制

Introspection 内省机制 ，也就是说通过指定id是什么类型 响应什么方法 通过if进行判断！

关于内省机制的方法：

• isKindOfClass：是否是这个类或者子类（类包括继承）
• isMemberOfClass: 是否是这个类（类不包括继承）
• responsToSelector：是否是类中的某个方法
• performSelector: 执行方法

[obj performSelector:shootSelector];
[obj performSelector:shootAtSelector withObject:coordinate];

[array makeObjectsPerformSelector:shootSelector];//让数组所有元素执行
[array makeObjectsPerformSelector:shootAtSelector withObject:target];

协议机制：

id <UIScrollViewDelegate> scrollViewDelegate;

使它能够对尖括号中的定义的这一组方法做出回应

@interface Vehicle
- (void)move;
@end

@interface Ship : Vehicle
- (void)shoot;
@end

Ship *s = [[Ship alloc] init];
[s shoot];
[s move];

Vehicle *v = s;
[v shoot]  #Would not crash at runtime. But have a Complier warning!

id

Foundatin Framwork

NSObject

-(id)copy;

语义：如果可能，返回该对象的一个不可变副本，如果NSDictionary,NSArray 利用copy是正确的，如果传递一个可变的数组、字典，那么返回的就是一个不可变的类。

-(id)mutableCopy;

语义：不管接收可变或者不可变，都返回可变的。

NSArray

不要利用下面的方法进行for in遍历:

NSArray *myArray = ...;
for (NSString *string in myArray){//数组元素可能不包含NSString类型
    double value = [string doubleValue];
    // Crash here if string is not an NSString
}

通过Introspection方式进行防御式编程：

NSArray *myArray = ...;
for (id obj in myArray){
    if([obj isKindOfClass:[NSString class]]){
        // send NSString messages to obj with no worries.
    }
}

NSNumber

创建NSNumber old方法：

NSNumber *n = [NSNumber numberWithInt:];
float f = [n floatValue];

新的语法创造NSNumber in iOS 6 : @()

NSNumber *three = @;
NSNumber *underline = @(NSUnderlineStyleSingle);
NSNumber *match = @([card match:@[otherCard]]);

NSDictionary

枚举遍历的方式：

NSDictionary *myDictionary = ...;
for (id key in myDictionary){
    // do something with key here
    id value = [myDictionary objectForKey:key];
    // do something with value here
}

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