将C++函数封装为块

Question

在我的应用程序中，我有一个C++类和一个Objective类，它们一起工作的方式如下：

PingPong.h

#ifndef __RSSCPPCallbackTest__PingPong__h
#define __RSSCPPCallbackTest__PingPong__h

#include <iostream>

class PingPong
{
public:
    static void requestPingPongWithText(std::string text);
    static void eventRequestPingPongWithTextSuccess(std::string successString);
    static void eventRequestPingPongWithTextFailure(std::string failureString);
};

#endif

PingPong.cpp

#ifndef __RSSCPPCallbackTest__PingPong__m
#define __RSSCPPCallbackTest__PingPong__m

#include "PingPong.h"

void PingPong::requestPingPongWithText(std::string text)
{
    if (text.compare("ping") == 0)
    {
        PingPong::eventRequestPingPongWithTextSuccess("success ping");
    }
    else
    {
        PingPong::eventRequestPingPongWithTextFailure("failure pong");
    }
}

#endif

目标-C类: MainViewController.mm

@implementation MainViewController

        /* init, viewDidLoad, etc... */

        // Call ping with a button
        - (IBAction)sayPing:(id)sender {

            NSString *text = @"ping";

            PingPong::requestPingPongWithText([text UTF8String]);
        }

        // Call pong with another button
        - (IBAction)sayPong:(id)sender {

            NSString *text = @"pong";

            PingPong::requestPingPongWithText([text UTF8String]);
        }    

@end

        void PingPong::eventRequestPingPongWithTextSuccess(std::string successString)
        {
            NSLog(@"successString: %@", [NSString stringWithCString:successString.c_str()
                                                           encoding:[NSString defaultCStringEncoding]]);
        }
        void PingPong::eventRequestPingPongWithTextFailure(std::string failureString)
        {
            NSLog(@"failureString: %@", [NSString stringWithCString:failureString.c_str()
                                                           encoding:[NSString defaultCStringEncoding]]);
        }

这个很好用。最后，我要做的是将它包装成一个函数，其中包含如下所示的完成块：

    [self requestPingPongWithText: text
    completion:^(NSString *successString, NSString *failureString)) completion {
     if (successString) {
NSLog(@"successString: %@", successString); } 
    else if (failureString) { 
NSLog(@"failureString: %@", failureString); }
    }];

我如何包装我现有的代码，使函数如上面所示？

Answer 1

让我们在Lets Pong.h中做一个新的类型：

typedef void (^OnComplete)(std::string successString, std::string failureString);

按块为请求创建一个新方法：

static void requestPingPongWithBlock(std:string text, OnComplete block);

另一种方法是，将其明确化：

static void requestPingPongWithBlock(std:string text, void (^block)(std::string successString, std::string failureString));

在PingPong.cpp中实现：

void PingPong::requestPingPongWithBlock(std::string text, OnComplete block)
{
    if (text.compare("ping") == 0)
    {
        block("success ping", "");
    }
    else
    {
        block("", "failure pong");
    }   
}

在MainViewController.mm中

-(void)requestPingPongWithText:(NSString*)text completion:(OnComplete) compblock{
    PingPong::requestPingPongWithBlock([text UTF8String],compblock);
}

你可以这样称呼它：

[self requestPingPongWithText: text
                   completion:^(std::string successString, std::string failureString) {
                       if (successString.length() != 0) {
                           NSLog([NSString stringWithUTF8String: successString.c_str()]); }
                       else if (failureString.length() != 0) {
                           NSLog([NSString stringWithUTF8String: failureString.c_str()]); }
                   }];

我希望这是有帮助的;)