Ccmenuitemfont a strange problem (method signature argument cannot be nil)

When studying a cocos2d demo tonight, I found the following line:CodeError

Ccmenuitemfont * fontlabel = [ccmenuitemfont itemfromstring: @ "Click me" Block: ^ (ID sender) {nslog (@ "test");}];

Error message: "Method signature argument cannot be nil"

However, this code can be used normally in another project, which makes me very puzzled ..

So I found a solution for my dog and recorded it.

Click here to view the solution

But the specific reason is not clear, it seems that a problem occurs when blocks is converted to SEL .. I am not clear about the solution. I hope some experts can answer this question...