#import <UIKit/UIKit.h>

@interface UIView (VCHFrame)

- (BOOL)isShowingOnKeyWindow;

@end

- (BOOL)isShowingOnKeyWindow {
    UIWindow *window = [UIApplication sharedApplication].keyWindow;
    CGRect newRect = [window convertRect:self.frame fromView:self.superview];
    BOOL intersects = CGRectIntersectsRect(newRect, window.bounds);
    return intersects && !self.isHidden && (self.alpha > 0.01) && (self.window == window);
}
~~~   

### 判断控制器是否显示到当前窗口   
可以用一种简单的方法，判断view是否已经加载，再判断window是否存在。用这两个条件正常情况下都可以判断出来。   
**这种方法不是绝对的。**

~~~ objc
- (BOOL)isShowing {
	return self.isViewLoaded && self.view.window;
}

- (NSComparisonResult)compare:(NSString *)string options:(NSStringCompareOptions)mask;

NSString *str0 = @"F0FF23FF";
NSString *str1 = @"F0FF023FF";
NSLog(@"%@ compare %@ == %zd", str0, str1, [str0 compare:str1 options:NSNumericSearch]);
//log : F0FF23FF compare F0FF023FF == 0
//理解：compare方法内部可以理解为把两个字符串拆分成
//F0FF23FF  --> F 0 FF  23 FF
//F0FF023FF --> F 0 FF 023 FF
//结果等于:0(两者相等)
//说明这个方法会将相邻的数字当成一个整体

str0 = @"E0FF23FF";
str1 = @"F0FF23FF";
NSLog(@"%@ compare %@ == %zd", str0, str1, [str0 compare:str1 options:NSNumericSearch]);
//log : E0FF23FF compare F0FF23FF == -1
//理解：compare方法内部可以理解为把两个字符串拆分成
//E0FF23FF --> E 0 FF 23 FF
//F0FF23FF --> F 0 FF 23 FF
// E < F , 结果等于:-1(前者小于后者)
//说明非数字也会进行比较

str0 = @"EF0FF23FF";
str1 = @"F0FF23FF";
NSLog(@"%@ compare %@ == %zd", str0, str1, [str0 compare:str1 options:NSNumericSearch]);
//log : EF0FF23FF compare F0FF23FF == -1
//理解：compare方法内部可以理解为把两个字符串拆分成
//EF0FF23FF --> EF 0 FF 23 FF
//F0FF23FF  --> F  0 FF 23 FF
//从左到右进行比较，E < F , 结果等于:-1(前者小于后者)
//说明此处是将"EF"中的"E" 和 "F" 比较，非数字不当成一个整体

str0 = @"E1FF23FF";
str1 = @"F0FF23FF";
NSLog(@"%@ compare %@ == %zd", str0, str1, [str0 compare:str1 options:NSNumericSearch]);
//log : E1FF23FF compare F0FF23FF == -1
//理解：compare方法内部可以理解为把两个字符串拆分成
//E0FF23FF --> E 1 FF 23 FF
//F0FF23FF --> F 0 FF 23 FF
//说明从左到右开始判断，数字有没优先权

str0 = @"1";
str1 = @".1";
NSLog(@"%@ compare %@ == %zd", str0, str1, [str0 compare:str1 options:NSNumericSearch]);
//log : 1 compare .1 == 1
//理解：compare方法内部可以理解为把两个字符串拆分成
//1 -->  0 1
//.1 --> . 1
//空格处应该不补充了一个数字，"."的ASCII码小于补充数字0的ASCII码。结果等于:1(前者大于后者)

str0 = @"1";
str1 = @":1";
NSLog(@"%@ compare %@ == %zd", str0, str1, [str0 compare:str1 options:NSNumericSearch]);
//log : 1 compare :1 == -1
//1 -->  0 1
//.1 --> : 1
//空格处应该不补充了一个数字，":"的ASCII码大于补充数字0的ASCII码。结果等于:-1(前者小于后者)

//
//  NSString+VCHProperty.h
//  SmartWatch
//
//  Created by chenhui on 2016/11/22.
//  Copyright © 2016年 vhuichen. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface NSString (VCHProperty)

- (NSUInteger)convertToByteLength;
- (NSUInteger)asciiLength;

@end

//
//  NSString+VCHProperty.m
//  SmartWatch
//
//  Created by chenhui on 2016/11/22.
//  Copyright © 2016年 vhuichen. All rights reserved.
//

#import "NSString+VCHProperty.h"

@implementation NSString (VCHProperty)

- (NSUInteger)convertToByteLength {
    NSUInteger selfLength = 0;
    char *p = (char *)[self cStringUsingEncoding:NSUnicodeStringEncoding];
    NSUInteger encodingLength = [self lengthOfBytesUsingEncoding:NSUnicodeStringEncoding];
    for (int i = 0; i < encodingLength; i++) {
        if (*p) {
            selfLength++;
        }
        p++;
    }
    return selfLength;
}

- (NSUInteger)asciiLength {
    NSUInteger selflLength = 0;
    for (int i = 0; i < self.length; i++) {
        unichar uc = [self characterAtIndex:i];
        selflLength += isascii(uc) ? 1 : 2;
    }
    return selflLength;
}

@end