当维度在类实例化时未定义时，如何在 Objective-C 中将浮点数组声明为类变量？
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原文地址: http://stackoverflow.com/questions/405426/
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How to declare an array of floats as a class variable in Objective-C when the dimension is undefined at the class instantiation time?
提问by Ariel Malka
In Java, it would look like this:
在 Java 中，它看起来像这样：
class Foo
{
float[] array;
}
Foo instance = new Foo();
instance.array = new float[10];
回答by Adam Rosenfield
You can just use a pointer:
你可以只使用一个指针：
float *array;
// Allocate 10 floats -- always remember to multiple by the object size
// when calling malloc
array = (float *)malloc(10 * sizeof(float));
...
// Deallocate array -- don't forget to do this when you're done with your object
free(array);
If you're using Objective-C++, you could instead do:
如果您使用的是 Objective-C++，则可以改为：
float *array;
array = new float[10];
...
delete [] array;
回答by Chris Lundie
Here's another way to do it. Create a NSMutableArray object and add NSNumber objects to it. It's up to you to decide whether or not this is sensible.
这是另一种方法。创建一个 NSMutableArray 对象并向其添加 NSNumber 对象。这是否合理由您来决定。
NSMutableArray *array;
array = [[NSMutableArray alloc] init];
[array addObject:[NSNumber numberWithFloat:1.0f]];
[array release];
回答by pcbeard
Another way to do this in Objective-C is to use indexed instance variables:
在 Objective-C 中执行此操作的另一种方法是使用索引实例变量：
@interface ArrayOfFloats : NSObject {
@private
NSUInteger count;
float numbers[0];
}
+ (id)arrayOfFloats:(float *)numbers count:(NSUInteger)count;
- (float)floatAtIndex:(NSUInteger)index;
- (void)setFloat:(float)value atIndex:(NSUInteger)index;
@end
@implementation ArrayOfFloats
+ (id)arrayOfFloats:(float *)numbers count:(NSUInteger)count {
ArrayOfFloats *result = [NSAllocateObject([self class], count * sizeof(float), NULL) init];
if (result) {
result->count = count;
memcpy(result->numbers, numbers, count * sizeof(float));
}
return result;
}
...
@end
For more see the documentation for NSAllocateObject(). A limitation of indexed instance variables is that you can't subclass a class that uses them.
有关更多信息，请参阅NSAllocateObject()的文档。索引实例变量的一个限制是你不能对使用它们的类进行子类化。
