传出参数 [英] passing out parameter

问题描述

我用out参数编写了一个方法：

I wrote a method with an out parameter:

-(NSString *)messageDecryption:(NSString *)receivedMessage outParam:(out)messageCondent
{   
    messageCondent = [receivedMessage substringFromIndex:2];
    return [receivedMessage substringToIndex:1];
}

然后我通过了这样的参数：

Then I passed the param like this:

NSString *messageCondent;
NSString *mode = [myclassobject messageDecryption:message outParam:messageCondent];

但是，有一个问题。 out参数值未正确设置。任何人都可以帮我正确地做到这一点吗？

However, there is a problem. The out parameter value is not being set properly. Can any one help me to do this correctly?

推荐答案

创建接受指向对象的指针的方法。

Create the method to accept a pointer to the object.

-(NSString *)messageDecryption:(NSString *)receivedMessage outParam:(NSString**)messageCondent
{   
    *messageCondent = [receivedMessage substringFromIndex:2];
    return [receivedMessage substringToIndex:1];

}

传入对本地对象的引用。

Pass in the reference to the local object.

NSString *messageCondent = nil;
NSString *mode = [myclassobject messageDecryption:message outParam:&messageCondent];

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