NSNumber十进制转换为C原始值？

Question

I want to convert a decimal NSNumber to an int or other form which I can do math with. Here's the annotated code for my project:

NSNumber *Left = [left valueForOutputKey:@"Y"];

This line gets a Quartz Composer Outlet, usually with a value around 0.512.

Basically, I want to multiply this by 10, and then do some operations like greater than and less than to see which range it is in.

Answer 1

Since it looks like you're dealing with a fractional component, you want to convert it to a float or a double to perform your operations, depending on how big you expect that value to be. A float should be fine unless you're dealing with ridiculously large or precise numbers. Here's how it would look, for example:

float lValue = [[left valueForOutputKey:@"Y"] floatValue];

lValue *= 10;

if (lValue < 10) {
    // do whatever
}
else if (lValue > 50) {
    // do whatever
}

Then to store the value back in your outlet or whatever, you pack it back into a NSNumber:

NSNumber *newValue = [NSNumber numberWithFloat:lValue];

[left setValue:newValue forKey:@"Y"];

You may have to convert newValue into a string to display it in a control, just use [newValue stringValue] to do that.

Answer 2

Use one of the methods of NSNumber :

int leftInt = [Left intValue];
float leftFloat = [Left floatValue];
double leftDouble = [Left doubleValue];