三元运算符用法？(Ternary operator usages?)

 您需要确保为自定义类定义了一个好的isEqual:方法，因为这是NSArray用来确定包含的内容： https ： //developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation / Classes / NSArray_Class /＃// apple_ref / occ / instm / NSArray / containsObject ： 
 
 假设这个类有类似'key'或'id'的值，对于每个类的实例（在你的例子中是double类型）是唯一的。 当然，情况并非总是如此; 它通常是个别属性/ ivars的集合，构成一个独特的“关键”，但为了讨论的目的，让我们说这样一个领域存在。 您的代码可能看起来像这样（全部在.m ）： 
 
static double const EPSILON = .000000001; // You'll need to be the judge of how "close" values can be to each other but still be distinct

@interface MyObjectClass: NSObject
@property (nonatomic, readonly) double uniqueKey;
@end

@implementation MyObjectClass

// ...

- (BOOL)isEqual:(id)object
{
    if (self == object) { return YES; }
    if (!object isKindOfClass:[MyObjectClass class]]) { return NO; }

    MyObjectClass *myObject = (MyObjectClass *)object;
    if (abs(self.uniqueKey - myObject.uniqueKey) < EPSILON) { return YES; }
    return NO;
}

//...

@end
 
 请注意，您不应检查两个float或double值之间的直接相等性; 看比较浮点值有多危险？ 有关使用浮点和双精度值的陷阱的良好讨论。 

You'll need to make sure you have a good isEqual: method defined for your custom class, since that's what NSArray uses to determine containment: https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSArray_Class/#//apple_ref/occ/instm/NSArray/containsObject:
 
Let's say this class has something like a 'key' or 'id' value that is unique for each instance of the class (which in your case is a double type). This will not always be the case, of course; it's often an aggregate of individual properties/ivars that constitutes a unique 'key', but for the purposes of this discussion let's say that such a field exists. Your code might look something like this (all in the .m):
 
static double const EPSILON = .000000001; // You'll need to be the judge of how "close" values can be to each other but still be distinct

@interface MyObjectClass: NSObject
@property (nonatomic, readonly) double uniqueKey;
@end

@implementation MyObjectClass

// ...

- (BOOL)isEqual:(id)object
{
    if (self == object) { return YES; }
    if (!object isKindOfClass:[MyObjectClass class]]) { return NO; }

    MyObjectClass *myObject = (MyObjectClass *)object;
    if (abs(self.uniqueKey - myObject.uniqueKey) < EPSILON) { return YES; }
    return NO;
}

//...

@end
 
Note that you should NOT check for direct equality between two float or double values; see How dangerous is it to compare floating point values? for a good discussion about the pitfalls of working with floating point and double precision values.