c++ - 将 C++ 函数包装成 block

Question

在我的应用程序中，我有一个 C++ 类和一个 Objective-c 类，按以下方式协同工作:

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

Objective-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]]);
        }

这很好用。我最终想做的是将其包装到一个带有完成 block 的函数中，如下所示:

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

我如何包装现有的代码以获得如上所示的函数？

Answer 1

让我们在 PingPong.h 中创建一个新的 typedef:

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

通过 block 为请求创建一个新方法:

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

另一种方式，使其明确:

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

PingPong.cpp 中的实现:

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

在MainViewController.mm

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

你可以这样调用它:

[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()]); }
                   }];

希望对您有帮助;)