ios developer tiny share-20161014

今天讲ios的NSNumber，以及NSUInteger

Numbers Are Represented by Instances of the NSNumber Class

The NSNumber class is used to represent any of the basic C scalar types, including char, double, float, int, long, short, and the unsigned variants of each, as well as the Objective-C Boolean type, BOOL.

As with NSString, you have a variety of options to create NSNumber instances, including allocation and initialization or the class factory methods:

NSNumber *magicNumber = [[NSNumber alloc] initWithInt:42];NSNumber *unsignedNumber = [[NSNumber alloc] initWithUnsignedInt:42u];NSNumber *longNumber = [[NSNumber alloc] initWithLong:42l];NSNumber *boolNumber = [[NSNumber alloc] initWithBOOL:YES];NSNumber *simpleFloat = [NSNumber numberWithFloat:3.14f];NSNumber *betterDouble = [NSNumber numberWithDouble:3.1415926535];NSNumber *someChar = [NSNumber numberWithChar:'T'];

It’s also possible to create NSNumber instances using Objective-C literal syntax:

NSNumber *magicNumber = @42;NSNumber *unsignedNumber = @42u;NSNumber *longNumber = @42l;NSNumber *boolNumber = @YES;NSNumber *simpleFloat = @3.14f;NSNumber *betterDouble = @3.1415926535;NSNumber *someChar = @'T';

These examples are equivalent to using the NSNumber class factory methods.

Once you’ve created an NSNumber instance it’s possible to request the scalar value using one of the accessor methods:

int scalarMagic = [magicNumber intValue];unsigned int scalarUnsigned = [unsignedNumber unsignedIntValue];long scalarLong = [longNumber longValue];BOOL scalarBool = [boolNumber boolValue];float scalarSimpleFloat = [simpleFloat floatValue];double scalarBetterDouble = [betterDouble doubleValue];char scalarChar = [someChar charValue];

The NSNumber class also offers methods to work with the additional Objective-C primitive types. If you need to create an object representation of the scalar NSInteger and NSUInteger types, for example, make sure you use the correct methods:

NSInteger anInteger = 64;NSUInteger anUnsignedInteger = 100;NSNumber *firstInteger = [[NSNumber alloc] initWithInteger:anInteger];NSNumber *secondInteger = [NSNumber numberWithUnsignedInteger:anUnsignedInteger];NSInteger integerCheck = [firstInteger integerValue];NSUInteger unsignedCheck = [secondInteger unsignedIntegerValue];

All NSNumber instances are immutable, and there is no mutable subclass; if you need a different number, simply use another NSNumber instance.

Note: NSNumber is actually a class cluster. This means that when you create an instance at runtime, you’ll get a suitable concrete subclass to hold the provided value. Just treat the created object as an instance of NSNumber.