如果我创建一个@property并对其进行合成,并创建一个getter和setter,就像这样:
#import <UIKit/UIKit.h>
{
NSString * property;
}
@property NSString * property;
--------------------------------
@implementation
@synthesize property = _property
-(void)setProperty(NSString *) property
{
_property = property;
}
-(NSString *)property
{
return _property = @"something";
}
我认为这个电话正确吗
-(NSString *)returnValue
{
return self.property; // I know that this automatically calls the built in getter function that comes with synthesizing a property, but am I correct in assuming that I have overridden the getter with my getter? Or must I explicitly call my self-defined getter?
}
这个电话是一样的吗?
-(NSString *)returnValue
{
return property; // does this call the getter function or the instance variable?
}
这个电话是一样的吗?
-(NSString *)returnValue
{
return _property; // is this the same as the first example above?
}
最佳答案
您的代码有很多问题,其中最重要的是您无意中定义了两个不同的实例变量:property
和_property
。
Objective-C属性语法只是普通的旧方法和实例变量的简写。您应该从没有属性的示例开始:仅使用常规实例变量和方法:
@interface MyClass {
NSString* _myProperty;
}
- (NSString*)myProperty;
- (void)setMyProperty:(NSString*)value;
- (NSString*)someOtherMethod;
@end
@implementation MyClass
- (NSString*)myProperty {
return [_myProperty stringByAppendingString:@" Tricky."];
}
- (void)setMyProperty:(NSString*)value {
_myProperty = value; // Assuming ARC is enabled.
}
- (NSString*)someOtherMethod {
return [self myProperty];
}
@end
要将此代码转换为使用属性,只需将
myProperty
方法声明替换为属性声明。@interface MyClass {
NSString* _myProperty;
}
@property (nonatomic, retain) NSString* myProperty
- (NSString*)someOtherMethod;
@end
...
实现保持不变,并且工作相同。
您可以选择在实现中合成属性,这可以删除
_myProperty
实例变量声明和通用属性设置器:@interface MyClass
@property (nonatomic, retain) NSString* myProperty;
- (NSString*)someOtherMethod;
@end
@implementation MyClass
@synthesize myProperty = _myProperty; // setter and ivar are created automatically
- (NSString*)myProperty {
return [_myProperty stringByAppendingString:@" Tricky."];
}
- (NSString*)someOtherMethod {
return [self myProperty];
}
这些示例中的每个示例在操作方式上都是相同的,属性语法只是速记,使您可以编写更少的实际代码。
关于objective-c - @property和setters和getters,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/9541828/