- (void)doSomethingWithArgument:(ArgType)argument error:(NSError **)error
Swift automatically translates Objective-C methods that produce errors
into methods that throw an error according to Swift’s native error
handling functionality.
但是在我的项目中描述的方法叫做：
object.doSomething(argument: ArgType,error: NSErrorPointer)
此外,当我尝试使用它们时,它会抛出运行时异常：
let errorPtr = NSErrorPointer() object.doSomething(argumentValue,error: errorPtr)
解决方法
被翻译成在Swift中投掷方法.
原因是Cocoa方法总是使用返回值NO或nil
以指示方法的失败,而不仅仅是设置错误对象.
这被记录在
Using and Creating Error Objects：
Important: Success or failure is indicated by the return value of the method.
Although Cocoa methods that indirectly return error objects in the Cocoa error
domain are guaranteed to return such objects if the method indicates failure
by directly returning nil or NO,you should always check that the return
value is nil or NO before attempting to do anything with the NSError object.
例如,Objective-C接口
@interface OClass : NSObject NS_ASSUME_NONNULL_BEGIN -(void)doSomethingWithArgument1:(int) x error:(NSError **)error; -(BOOL)doSomethingWithArgument2:(int) x error:(NSError **)error; -(NSString *)doSomethingWithArgument3:(int) x error:(NSError **)error; -(NSString * _Nullable)doSomethingWithArgument4:(int) x error:(NSError **)error; NS_ASSUME_NONNULL_END @end
被映射到Swift as
public class OClass : NSObject {
public func doSomethingWithArgument1(x: Int32,error: NSErrorPointer)
public func doSomethingWithArgument2(x: Int32) throws
public func doSomethingWithArgument3(x: Int32,error: NSErrorPointer) -> String
public func doSomethingWithArgument4(x: Int32) throws -> String
}
如果您可以更改方法的界面,那么您应该添加一个布尔值
返回值表示成功或失败.
否则你会把它从Swift称为
var error : NSError?
object.doSomethingWithArgument(argumentValue,error: &error)
if let theError = error {
print(theError)
}
备注：
> https://github.com/apple/swift/blob/master/test/Inputs/clang-importer-sdk/usr/include/errors.h
我发现Clang有一个属性,强制一个函数在Swift中抛出一个错误：
-(void)doSomethingWithArgument5:(int) x error:(NSError **)error __attribute__((swift_error(nonnull_error)));
被映射到Swift as
public func doSomethingWithArgument5(x: Int32) throws
