背景介绍

今天做项目时候由于有个需求是需要对textField输入框进行内容和长度的限制，然后在网上找了大量的相关问题，都没有能够解决我的需求的，所以只能自己进行完善。

代码介绍

代码完成了针对输入内容的实时监听，并且完成了和键盘配套的复制来的内容的限制，所以本套代码可以实现输入框内完整干净的限制。

代码实现

本代码是在textfield的类目中实现的，所以请需要的自行完善，或询本人。
.h

#import <UIKit/UIKit.h>

@interface UITextField (ZG_LengthLimit)

@property (nonatomic,strong)NSNumber *MAXLENGTH;//传入Integer类型的数据，

- (void)addObserverTextChangeWithMAXLENGTH:(NSInteger)MAXLENGTH;

@end

.m

#import "UITextField+ZG_LengthLimit.h"
#import <objc/runtime.h>


@implementation UITextField (ZG_LengthLimit)

- (void)setMAXLENGTH:(NSNumber *)_MAXLENGTH {
    objc_setAssociatedObject(self, @"MAXLENGTH", _MAXLENGTH, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (NSNumber *)MAXLENGTH {
    return objc_getAssociatedObject(self, @"MAXLENGTH");
}

- (void)addObserverTextChangeWithMAXLENGTH:(NSInteger)MAXLENGTH{
    self.MAXLENGTH = [NSNumber numberWithInteger:MAXLENGTH];
    [self addTarget:self action:@selector(textFieldDidChange:) forControlEvents:UIControlEventEditingChanged];
    
}
- (void)textFieldDidChange:(id)sender
{
    UITextField *textField = self;
    NSString *toBeString = textField.text;
    
        //获取高亮部分
    UITextRange *selectedRange = [textField markedTextRange];
    UITextPosition *position1 = [textField positionFromPosition:selectedRange.start offset:0];
    
        // 没有高亮选择的字，则对已输入的文字进行字数统计和限制
    if (!position1 || !selectedRange)
        {
        NSString *patth = [self getPattern];
        if (patth) {
            toBeString = [self stringisMyNeed:self.text andPattern:patth];
            textField.text = toBeString;
        }
        if (toBeString.length > [self.MAXLENGTH integerValue])
            {
            NSRange rangeIndex = [toBeString rangeOfComposedCharacterSequenceAtIndex:[self.MAXLENGTH integerValue]];
            if (rangeIndex.length == 1)
                {
                textField.text = [toBeString substringToIndex:[self.MAXLENGTH integerValue]];
                }
            else
                {
                NSRange rangeRange = [toBeString rangeOfComposedCharacterSequencesForRange:NSMakeRange(0, [self.MAXLENGTH integerValue])];
                textField.text = [toBeString substringWithRange:rangeRange];
                }
            }
        }
    
}

/*
 UIKeyboardTypeDefault,                 all
 UIKeyboardTypeASCIICapable,            [0-9]|[A-Za-z]
 UIKeyboardTypeNumbersAndPunctuation,   [A-Za-z]|[\u4e00-\u9fa5]
 UIKeyboardTypeURL,                     all
 UIKeyboardTypeNumberPad,               [0-9]
 UIKeyboardTypePhonePad,                [0-9]
 UIKeyboardTypeNamePhonePad,            all
 UIKeyboardTypeEmailAddress,            all
 UIKeyboardTypeDecimalPad NS_ENUM_AVAILABLE_IOS(4_1),           [0-9]
 UIKeyboardTypeTwitter NS_ENUM_AVAILABLE_IOS(5_0),              all
 UIKeyboardTypeWebSearch NS_ENUM_AVAILABLE_IOS(7_0),            all
 UIKeyboardTypeASCIICapableNumberPad NS_ENUM_AVAILABLE_IOS(10_0), [0-9]
 UIKeyboardTypeAlphabet = UIKeyboardTypeASCIICapable,   [0-9]|[A-Za-z]
 */

- (NSString *)getPattern{
    NSString *patternStr;
    switch (self.keyboardType) {
        case UIKeyboardTypeDefault:
            patternStr = nil;
            break;
        case UIKeyboardTypeASCIICapable:
            patternStr = @"[0-9]|[A-Za-z]";
            break;
        case UIKeyboardTypeNumbersAndPunctuation:
            patternStr = @"[A-Za-z]|[\u4e00-\u9fa5]";
            break;
        case UIKeyboardTypeURL:
            patternStr = nil;
            break;
        case UIKeyboardTypeNumberPad:
            patternStr = @"[0-9]";
            break;
        case UIKeyboardTypePhonePad:
            patternStr = @"[0-9]";
            break;
        case UIKeyboardTypeNamePhonePad:
            patternStr = nil;
            break;
        case UIKeyboardTypeEmailAddress:
            patternStr = nil;
            break;
        case UIKeyboardTypeDecimalPad:
            patternStr = @"[0-9]";
            break;
        case UIKeyboardTypeTwitter:
            patternStr = nil;
            break;
        case UIKeyboardTypeWebSearch:
            patternStr = nil;
            break;
        case UIKeyboardTypeASCIICapableNumberPad:
            patternStr = @"[0-9]";
            break;
        default:
            patternStr = nil;
            break;
    }
    return patternStr;
}

- (NSString *)stringisMyNeed:(NSString *)str andPattern:(NSString *)pattern{
    
    NSRange range;
    for(int i=0; i<str.length; i+=range.length){
        range = [str rangeOfComposedCharacterSequenceAtIndex:i];
        NSString *s = [str substringWithRange:range];
        BOOL isdel = [self isNeed:s WithPattern:pattern];
        if (!isdel) {
            str = [str stringByReplacingCharactersInRange:range withString:@""];
            i-=range.length;
        }
    }
    return str;
}

- (BOOL)isNeed:(NSString *)str WithPattern:(NSString *)pattern{
        //[0-9]|[A-Za-z]|[\u4e00-\u9fa5]
    NSRegularExpression *tLetterRegularExpression = [NSRegularExpression regularExpressionWithPattern:pattern options:NSRegularExpressionCaseInsensitive error:nil];
    
    NSUInteger tLetterMatchCount = [tLetterRegularExpression numberOfMatchesInString:str options:NSMatchingReportProgress range:NSMakeRange(0, str.length)];
    NSLog(@"%ld",tLetterMatchCount);
    if(tLetterMatchCount>=1){
        return YES;
    }else{
        return NO;
    }
}

以上为全部代码。
其中注释部分为对应键盘的正则，目前只做了数字，字母，汉字的。有其他需求的可以自行加入
有问题可以留言。
谢谢。

参考网址：
http://www.jianshu.com/p/2d1c06f2dfa4
http://www.cnblogs.com/sunnyke/p/4665248.html