iOS development--Practical Technology OC Chapter & Add attribute to category

Add attributes to a category

About the creation of classifications we're going to do this right here.

Here is an example of text-based color for placeholder text
One: Simple Way (Key technology: KVC)
1. Define a property in the header file

 1  @property (nonatomic, strong) Uicolor * 2  *  3   * classification only produces declarations of attributes corresponding to setter and getter methods, no implementation, We need to implement the  4  */ 5  // -(void) Setplaceholdercolor: ( Uicolor *) Placeholdercolor;  6  -( Uicolor *) Placeholdercolor;  

2. Define a static constant for the settings of the following properties
1 static NSString * const Placeholdercolorkey = @ " Placeholderlabel.textcolor";

3. Implement setter and Getter properties for this property (System will not be implemented in the classification)

1-(void) Setplaceholdercolor: (Uicolor *) Placeholdercolor2 {3BOOL change =NO;4     5     if(Self.placeholder = =Nil) {6Self.placeholder =@" ";7Change =YES;8     }9     Ten [self setvalue:placeholdercolor forkeypath:placeholdercolorkey]; One      A     if(change) { -Self.placeholder =Nil; -     } the } -  --(Uicolor *) Placeholdercolor - { +     return[self valueforkeypath:placeholdercolorkey]; -}

Two: Loading mode (Key technology: Runtime)

1. Define a property in the header file

1 @property (nonatomic, strong) Uicolor *placeholdercolor;

2. Import the run-time library

1 #import <objc/runtime.h>

Implement Setterg and Getter methods to correlate data using management Object technology

1-(void) Setplaceholdercolor: (Uicolor *) Placeholdercolor2 {3     /**4 * Related objects: 15      */6Objc_setassociatedobject (Self, &Placeholdercolorkey, Placeholdercolor, objc_association_assign);7 }8 9-(Uicolor *) PlaceholdercolorTen { One     /** A * Related objects: 2 -      */ -      returnObjc_getassociatedobject (Self, &placeholdercolorkey); the}

More about the operation of the relevant technology to see the author earlier related articles

iOS development--Practical Technology OC Chapter & Add attribute to category