如何在Swift中正确打印块参数?

I see the following discrepancy in Playgrounds for Swift 1.2 and 2.0 when I want to print the value of a parameter in a block I am passing as input to a function. Any help in understanding what is going on would be appreciated!

当我想在我传递给函数的块中打印参数的值时，我看到了Swift 1.2和2.0的不同之处。任何有助于理解正在发生的事情的帮助都是值得感激的!

func blockSample(myInput: String, myOutput: (answer: String) -> ()) {
    myOutput(answer: myInput)
}

blockSample("testthis") { (answer) -> () in
    print(answer) // This should print "testthis" but it doesn't
}

blockSample("testthis") { (answer) -> () in
    print("test") // print something before the next line
    print(answer) // this works. prints "testthis"
}

blockSample("testthis") { (answer) -> () in
    let printedAnswer = answer
    print(answer) // this works. prints "testthis". Note that I am printing answer and not printedAnswer
}

1 个解决方案

#1

Your first example indeed doesn't print in the live panel of the Playground contrary to the others.

你的第一个例子实际上并没有在操场的活动面板上打印，与其他的相反。

But with Xcode 7 Playgrounds if you open the menu:

但是如果你打开菜单的话，有Xcode 7的游戏场:

View / Debug Area / Show Debug Area

查看/调试区域/显示调试区域

you will see in the console that everything is printed properly.

您将在控制台看到，所有内容都被正确地打印出来。

In Xcode 6 Playgrounds you can achieve the same by displaying the Assistant Editor:

在Xcode 6游戏场中，你可以通过显示助理编辑器来达到同样的效果:

View / Assistant Editor / Show Assistant Editor

视图/辅助编辑器/显示助理编辑器。

Also, remember that in Playgrounds you can force the display of a value in the live panel by just stating your variable on a separate line:

另外，请记住，在操场上，您可以通过在另一行上声明变量来强制显示活动面板中的值:

blockSample("testthis") { (answer) -> () in
    answer  //  this will force the live display of the value for 'answer'
    print(answer)
}

#1