对象：正确使用属性并进行合成？

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有人知道为什么这段代码会遇到编译错误吗？我正在使用clang在Catalina上进行编译。我在此处发布了类似的问题，那是我尝试使用在Linux上发出叮当声。我以为getA和setA是由synthesize自动生成的。谢谢！

Does anyone know why this code is running into compilation errors? I'm compiling it on Catalina using clang. I posted a similar issue here but that was when I was trying to compile using clang on Linux. I thought getA and setA are auto-generated by synthesize. Thanks!

#import <Foundation/Foundation.h> @interface A: NSObject @property int a; @end @implementation A { int a; } @synthesize a; @end int main (int argc, char * argv[]) { @autoreleasepool { A *a = [[A alloc] init]; [a setA:99]; int v = [a getA]; NSLog (@" %d\n", v); } return 0; }

编译：

$ clang -framework Foundation otest0.m -o hello otest0.m:23:16: warning: instance method '-getA' not found (return type defaults to 'id') [-Wobjc-method-access] int v = [a getA]; ^~~~ otest0.m:3:12: note: receiver is instance of class declared here @interface A: NSObject ^ otest0.m:23:9: warning: incompatible pointer to integer conversion initializing 'int' with an expression of type 'id' [-Wint-conversion] int v = [a getA]; ^ ~~~~~~~~ 2 warnings generated.

推荐答案

getter / setter对合成为

The getter/setter pair is synthesized as

-(int)a; -(void)setA:(int)val;

所以您需要：

int main (int argc, char * argv[]) { @autoreleasepool { A *a = [[A alloc] init]; [a setA:99]; int v = [a a]; NSLog (@" %d\n", v); } return 0; }