Uitextview implementation of placeholder functions

In iOS we Uitextfield have placeholder function, but Uitextview does not have this method, sometimes we also need to implement such placeholder function, StackOverflow gives us a way to rewrite the Uitextview, a small amount of code to achieve this function, it is worth learning.

#import <UIKit/UIKit.h> @interface Uiplaceholdertextview:uitextview@property (nonatomic, retain) NSString * placeholder; @property (nonatomic, retain) Uicolor *placeholdercolor;-(void) textChanged: (nsnotification*) notification; @end

#import "UIPlaceHolderTextView.h" @interface Uiplaceholdertextview () @property (nonatomic, retain) UILabel * Placeholderlabel, @end @implementation uiplaceholdertextviewcgfloat const Ui_placeholder_text_changed_animation_ DURATION = 0.25;-(void) dealloc{[[Nsnotificationcenter Defaultcenter] removeobserver:self]; #if __has_feature (objc_ ARC) #else [_placeholderlabel release];    _placeholderlabel = nil; [_placeholdercolor release];    _placeholdercolor = nil; [_placeholder release];    _placeholder = nil;        [Super Dealloc]; #endif}-(void) awakefromnib{[Super awakefromnib]; Use Interface Builder User Defined Runtime Attributes to set//placeholder and placeholdercolor in Interface Builde    R. if (!self.placeholder) {[Self setplaceholder:@ "];    } if (!self.placeholdercolor) {[self setplaceholdercolor:[uicolor lightgraycolor]]; } [[Nsnotificationcenter defaultcenter] addobserver:self selector: @selector (textChanged:) Name:uitextviewtextdidchaNgenotification Object:nil];}        -(ID) initWithFrame: (CGRect) frame{if (self = [super Initwithframe:frame])} {[Self setplaceholder:@ "];        [Self Setplaceholdercolor:[uicolor lightgraycolor]]; [[Nsnotificationcenter Defaultcenter] addobserver:self selector: @selector (textChanged:) Name:    Uitextviewtextdidchangenotification Object:nil]; } return self;}    -(void) textChanged: (nsnotification *) notification{if ([[Self placeholder] length] = = 0) {return; } [UIView animatewithduration:ui_placeholder_text_changed_animation_duration animations:^{if ([[Self TEXT] L        Ength] = = 0) {[[Self viewwithtag:999] setalpha:1];        } else {[self viewwithtag:999] setalpha:0]; }    }];}    -(void) SetText: (NSString *) text {[Super Settext:text]; [Self textchanged:nil];}        -(void) DrawRect: (CGRect) rect{if ([[Self placeholder] length] > 0) {if (_placeholderlabel = = nil)       {     _placeholderlabel = [[UILabel alloc] Initwithframe:cgrectmake (8,8,self.bounds.size.width-16,0)];            _placeholderlabel.linebreakmode = nslinebreakbywordwrapping;            _placeholderlabel.numberoflines = 0;            _placeholderlabel.font = Self.font;            _placeholderlabel.backgroundcolor = [Uicolor Clearcolor];            _placeholderlabel.textcolor = Self.placeholdercolor;            _placeholderlabel.alpha = 0;            _placeholderlabel.tag = 999;        [Self Addsubview:_placeholderlabel];        } _placeholderlabel.text = Self.placeholder;        [_placeholderlabel SizeToFit];    [Self Sendsubviewtoback:_placeholderlabel];  if ([self text] length] = = 0 && [[self placeholder] length] > 0) {[[Self viewwithtag:999]    SETALPHA:1]; } [Super Drawrect:rect];} @end

Uitextview implementation of placeholder functions