实现UITextView的placeholder及限制输入次数（干货）

众所周知， UITextfield有一个属性可以设置其placeholder， 但是UITextView却没有， 所以往往遇到要设置它的占位字符时，都要百度一番~~ ，今天又遇到这个问题， 所以自己写了一个Catgorty来实现这个需求， 分享出来希望能帮助一些伙伴！ 好了， 话不多说， 上菜上菜

.h文件

@property (nonatomic,strong) NSString *placeholder;//占位符
@property (copy, nonatomic) NSNumber *limitLength;//限制字数

.m文件

@interface UITextView ()

@property (nonatomic,strong) UILabel *placeholderLabel;//占位符
@property (nonatomic,strong) UILabel *wordCountLabel;//计算字数

@end

@implementation UITextView (RSTextViewSetting)
static NSString *PLACEHOLDLABEL = @"placelabel";
static NSString *PLACEHOLD = @"placehold";
static NSString *WORDCOUNTLABEL = @"wordcount";
static const void *limitLengthKey = &limitLengthKey;

#pragma mark -- set/get...

-(void)setPlaceholderLabel:(UILabel *)placeholderLabel {

objc_setAssociatedObject(self, &PLACEHOLDLABEL, placeholderLabel, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (UILabel *)placeholderLabel {

return objc_getAssociatedObject(self, &PLACEHOLDLABEL);

}

- (void)setPlaceholder:(NSString *)placeholder {

objc_setAssociatedObject(self, &PLACEHOLD, placeholder, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
[self setPlaceHolderLabel:placeholder];
}

- (NSString *)placeholder {

return objc_getAssociatedObject(self, &PLACEHOLD);
}

- (UILabel *)wordCountLabel {

return objc_getAssociatedObject(self, &WORDCOUNTLABEL);

}
- (void)setWordCountLabel:(UILabel *)wordCountLabel {

objc_setAssociatedObject(self, &WORDCOUNTLABEL, wordCountLabel, OBJC_ASSOCIATION_RETAIN_NONATOMIC);

}

- (NSNumber *)limitLength {

return objc_getAssociatedObject(self, limitLengthKey);
}

- (void)setLimitLength:(NSNumber *)limitLength {
objc_setAssociatedObject(self, limitLengthKey, limitLength, OBJC_ASSOCIATION_COPY_NONATOMIC);
[self addLimitLengthObserver:[limitLength intValue]];

[self setWordcountLable:limitLength];

}

#pragma mark -- 配置占位符标签

- (void)setPlaceHolderLabel:(NSString *)placeholder {

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(textFieldChanged:) name:UITextViewTextDidChangeNotification object:self];
if (self.placeholderLabel) {
[self.placeholderLabel removeFromSuperview];
}
/*
*  占位字符
*/
self.placeholderLabel = [[UILabel alloc] init];
self.placeholderLabel.font = [UIFont systemFontOfSize:13.];
self.placeholderLabel.text = placeholder;
self.placeholderLabel.numberOfLines = 0;
self.placeholderLabel.lineBreakMode = NSLineBreakByWordWrapping;
self.placeholderLabel.textColor = UGUColorFromRGB_0x(0xD6D6D6);
CGRect rect = [placeholder boundingRectWithSize:CGSizeMake(CGRectGetWidth(self.frame)-7, CGFLOAT_MAX) options:NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName: [UIFont systemFontOfSize:13.]} context:nil];
self.placeholderLabel.frame = CGRectMake(7, 7, rect.size.width, rect.size.height);
[self addSubview:self.placeholderLabel];
self.placeholderLabel.hidden = self.text.length > 0 ? YES : NO;
self.wordCountLabel.text = [NSString stringWithFormat:@"%lu/%@",(unsigned long)self.text.length,self.limitLength];

}

#pragma mark -- 配置字数限制标签

- (void)setWordcountLable:(NSNumber *)limitLength {
if (self.wordCountLabel) {
[self.wordCountLabel removeFromSuperview];
}
/*
*  字数限制
*/
self.wordCountLabel = [[UILabel alloc] initWithFrame:CGRectMake(kWidth - 110, CGRectGetHeight(self.frame) - 35, 65, 35)];
self.wordCountLabel.textAlignment = NSTextAlignmentRight;
self.wordCountLabel.textColor = [UIColor lightGrayColor];
self.wordCountLabel.font = [UIFont systemFontOfSize:14];
if (self.text.length > [limitLength integerValue]) {
self.text = [self.text substringToIndex:[self.limitLength intValue]];
}
self.wordCountLabel.text = [NSString stringWithFormat:@"%lu/%@",(unsigned long)self.text.length,limitLength];
[self addSubview:self.wordCountLabel];

}

#pragma mark -- 增加限制位数的通知
- (void)addLimitLengthObserver:(int)length {

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(limitLengthEvent) name:UITextViewTextDidChangeNotification object:self];
}

#pragma mark -- 限制输入的位数
- (void)limitLengthEvent {

if ([self.text length] > [self.limitLength intValue]) {

self.text = [self.text substringToIndex:[self.limitLength intValue]];
}
}

#pragma mark -- NSNotification

- (void)textFieldChanged:(NSNotification *)notification {
if (self.placeholder) {
self.placeholderLabel.hidden = YES;

if (self.text.length == 0) {

self.placeholderLabel.hidden = NO;
}
}
if (self.limitLength) {

NSInteger wordCount = self.text.length;
if (wordCount > [self.limitLength integerValue]) {
wordCount = [self.limitLength integerValue];
}
self.wordCountLabel.text = [NSString stringWithFormat:@"%zd/%@",wordCount,self.limitLength];
}

}

- (void)dealloc {

[[NSNotificationCenter defaultCenter] removeObserver:self
name:UITextViewTextDidChangeNotification
object:self];
}

设置的时候，直接设置.h文件的两个属性即可！