Round Braffets Around＆＃34; Typedef＆＃34;数据类型

Question

圆括号对optionAction = attempter(option);行中的typedef做了什么？ 是那个演员？

完整代码：

- (id<ISFModalMessageView>)modalMessageWithError:(NSError *)error recoveryAttempter:(SFErrorRecoveryAttempter)attempter
{
if ([self shouldNotifyUserForError:error] && [self typeForError:error] == SFErrorTypeAlert) 
{ 
NSString *title = [self titleForError:error];
NSString *message = [self messageForError:error];
SFAlertMessageView *alert = [[SFAlertMessageView alloc]initWithTitle:title message:message image:nilcancelButton:@"Cancel"];

SFErrorRecoveryOption option = [self recoveryOptionForError:error];
if (option != SFErrorRecoveryOptionUndefiend) 
{ 
NSString *optionTitle = [self titleForRecoveryOptionOfError:error];     
SFModalMessageAction optionAction = nil;

if (attempter) {
optionAction = attempter(option);  // This Part
}
if (optionTitle.notEmpty && optionAction) {
[alert addActionButtonWithTitle:optionTitle action:optionAction];
} 
}
return alert;
}
return nil;
}

SFErrorRecoveryOption：

typedef NS_ENUM(NSUInteger, SFErrorRecoveryOption) {
SFErrorRecoveryOptionUndefiend = 0,

SFErrorRecoveryOptionTryAgain,
SFErrorRecoveryOptionReport,
SFErrorRecoveryOptionSignIn,
SFErrorRecoveryOptionSignUp,
SFErrorRecoveryOptionReset,
SFErrorRecoveryOptionSignInFacebook,
};

SFModalMessageAction：

typedef void (^ SFModalMessageAction)() ;

SFErrorRecoveryAttempter：

typedef SFModalMessageAction (^ SFErrorRecoveryAttempter)(SFErrorRecoveryOption option);

Answer 1

很可能SFErrorRecoveryAttempter是对某些block type的类型定义并且有问题的行

attempter(option);

只是调用作为参数传递给您的方法的块。请注意，调用nil块将导致异常，因此添加了if (attempter)检查