[英]How to filter CGPoints in an NSArray by CGRect
I have an NSArray
with CGPoints
. 我有一个带有
CGPoints
的NSArray
。 I'd like to filter this array by only including points within a rect. 我想通过在rect中包含点来过滤这个数组。
How can I formulate an NSPredicate
such that each point satisfies this predicate: 我如何制定一个
NSPredicate
,使每个点满足这个谓词:
CGRectContainsPoint(windowRect, point);
CGRectContainsPoint(windowRect,point);
Here's the code so far: 这是迄今为止的代码:
NSArray *points = [NSArray arrayWithObjects: [NSValue valueWithCGPoint:pointAtYZero] ,
[NSValue valueWithCGPoint:pointAtYHeight],
[NSValue valueWithCGPoint:pointAtXZero],
[NSValue valueWithCGPoint:pointAtXWidth],
nil];
NSPredicate *inWindowPredicate = [NSPredicate predicateWithFormat:@"CGRectContainsPoint(windowRect, [point CGPointValue])"];
NSArray *filteredPoints = [points filteredArrayUsingPredicate:inWindowPredicate];
You cannot do this with the predicate format syntax, but you can use a block: 您不能使用谓词格式语法执行此操作,但可以使用块:
NSArray *points = ...;
CGRect windowRect = ...;
NSPredicate *inWindowPredicate = [NSPredicate predicateWithBlock:^BOOL(id evaluatedObject, NSDictionary *bindings) {
CGPoint point = [evaluatedObject CGPointValue];
return CGRectContainsPoint(windowRect, point);
}];
NSArray *filteredPoints = [points filteredArrayUsingPredicate:inWindowPredicate];
Note that it's not possible to use block-based predicates for Core Data fetch requests. 请注意,无法对Core Data获取请求使用基于块的谓词。
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