如何解决“无法识别的选择器发送到实例”？ [英] How to resolve 'unrecognized selector sent to instance'?
问题描述
在AppDelegate中，我分配了一个在静态库中定义的实例。这个实例有一个NSString属性设置一个复制。当我访问此实例上的字符串属性时，应用程序崩溃，并显示无法识别的选择器发送到实例。 Xcode为属性提供了一个代码提示，这意味着它在调用应用程序中是已知的。特定的类被编译成静态库目标。我缺少什么？
In the AppDelegate, I'm alloc'ing an instance defined in a static library. This instance has an NSString property set a "copy". When I access the string property on this instance, the app crashes with 'unrecognized selector sent to instance'. Xcode provides a code hint for the property, which means it is known in the calling app. The particular class is compiled into the static library target. What am I missing?
添加一些代码。
//static library
//ClassA.h
@interface ClassA : NSObject {
...
NSString *downloadUrl;
}
@property(nonatomic, copy) NSString *downloadUrl;
//ClassA.m
@synthesize downloadUrl;
在致电应用程式的appDelegate中。
In the calling app's appDelegate.
//app delegate header file
@interface myApp : NSObject <UIApplicationDelegate> {
ClassA *classA;
}
@property (nonatomic, retain) ClassA *classA;
//app delegate .m file
@synthesize classA;
- (void)applicationDidFinishLaunching:(UIApplication *)application {
classA = [[ClassA alloc] init];
//exception occurs here. downloadUrl is of type NSCFNumber
classA.downloadUrl = @"http://www.abc.com/";
...}
应用程序中的其他类将获得对委托的引用，调用classA.downloadUrl。
Other classes in the app will get a reference to the delegate and call classA.downloadUrl.
推荐答案
1）是否在 @implementation block？
1) Is the synthesize within @implementation block?
2）你应该参考 self.classA = [[ClassA alloc] init]; self.classA.downloadUrl = @...而不是纯粹 classA ？
2) Should you refer to self.classA = [[ClassA alloc] init]; and self.classA.downloadUrl = @"..." instead of plain classA?
3）在 myApp.m 文件中，您需要导入 ClassA.h 当它缺少它会默认一个数字，或指针？ （在C变量中默认为int，如果编译器没有找到）：
3) In your myApp.m file you need to import ClassA.h, when it's missing it will default to a number, or pointer? (in C variables default to int if not found by compiler):
#importClassA.h。
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