Is there a constant for the maximum CGFloat value?

问题

I need to create a CGSize to compute text height of an arbitrary text with arbitrary length. UIKit has this nice method -sizeWithFont:constrainedToSize: and my text is only constrained in width, but not in height.

For this, I need to set the maximum possible CGFloat for the height.

Is there a constant like "CGFloatMax"?

回答1:

CGGeometry defines:

#define CGFLOAT_MAX FLT_MAX

回答2:

For those using Swift 2, you should use:

CGFloat.max

For those using Swift 3, you should use:

CGFloat.greatestFiniteMagnitude

Note that CGFloat.max was removed when Swift 3 came out, as reflected in the documentation.

回答3:

How about CGFLOAT_MAX?

回答4:

A CGFloat is just a float so you can safely use FLT_MAX from <float.h>.

EDIT: As others have now pointed out it looks like CGFLOAT_MAX is already defined for you so you should use that for consistency rather than FLT_MAX, even though they are the same thing on 32 bit platforms.

回答5:

I was looking for a Swift version of minimum CGFloat value and landed here, if you too ;) then here is the answer:

CGFloat.leastNormalMagnitude

回答6:

This is more of a comment than an answer however I don't have enough reputation to comment at the present.

I just came across unexpected behavior with using CGFLOAT_MAX: on an iPhone 5S (64bit) device running iOS 7.1.2 and using Xcode 5.1.1, the following code:

CGFloat numRot = floorf(CGFLOAT_MAX / 360.0);
NSLog(@"numRot = %.2f", numRot);

Outputs:

numRot = inf

Whereas, this code:

CGFloat numRot = floorf(FLT_MAX / 360.0);
NSLog(@"numRot = %.2f", numRot);

Correctly outputs:

numRot: 945228740662580166143622731901435904.00

I command+clicked on the CGFLOAT_MAX and Xcode took me to the CoreGraphics frameworks CGBase.h file with the following macro definition:

# define CGFLOAT_MAX DBL_MAX

I command+clicked on CGFloat and Xcode took me to another line in the same file:

typedef CGFLOAT_TYPE CGFloat;

Then I command+clicked on the CGFLOAT_TYPE and it jumped to the #define line here:

#if defined(__LP64__) && __LP64__
# define CGFLOAT_TYPE double
...

So, for some reason my CGFloat variable is supposed to be a double, however it appears to be a float that overflows when it gets assigned a double value (i.e. CGFLOAT_MAX). As far as I can tell this Apple documentation page indicates using %f with NSLog should print the double - someone please correct me if this is wrong.

All that to say, if FLT_MAX works for your case, you may want to stick with that for now instead of CGFLOAT_MAX, especially if you are relying on a library that specifically accept float arguments instead of double or CGFloat.

回答7:

CGSize size = CGSizeMake(CGFLOAT_MIN, CGFLOAT_MAX);

width = 0.0000000000000000000000000000000000000117549435, height = 3.40282347E+38

回答8:

In Swift 3.0, You can also use CGFloat(FLT_MAX), especially if you want to use it in other cases like zIndex, where CGFloat.greatestFiniteMagnitude will be out of range.

来源：https://stackoverflow.com/questions/6285188/is-there-a-constant-for-the-maximum-cgfloat-value