iOS UITextField的光标获取和设置

类拓展：代码如下

#import 

@interface UITextField (Add)
@property(nonatomic,assign) NSRange selectedRange;
@end

#import "UITextField+Add.h"

@implementation UITextField (Add)

-(NSRange)selectedRange{
    NSInteger location = [self offsetFromPosition:self.beginningOfDocument toPosition:self.selectedTextRange.start];
    NSInteger length = [self offsetFromPosition:self.selectedTextRange.start toPosition:self.selectedTextRange.end];
    return NSMakeRange(location, length);
}

-(void)setSelectedRange:(NSRange)selectedRange{
    UITextPosition *startPosition = [self positionFromPosition:self.beginningOfDocument offset:selectedRange.location];
    UITextPosition *endPosition = [self positionFromPosition:self.beginningOfDocument offset:selectedRange.location + selectedRange.length];
    UITextRange *selectedTextRange = [self textRangeFromPosition:startPosition toPosition:endPosition];
    [self setSelectedTextRange:selectedTextRange];
}

@end