Coding style of “if” statements [duplicate]

问题

Lately I've been noticing the style of some programmers who write "if" statements backwards. That is, in the test they put the constant value first and then the variable that they are testing second. So for example they write:

bar = foo();
if (MY_CONSTANT == bar) {
    /*  then do something */
}

To me, this makes code somewhat difficult to read. Since we are really talking about testing the value of the variable "bar" and not all variables that are equal to "MY_CONSTANT", I always put the variable first. Its sort of a unspoken grammar.

Anyhow, I see that some programmers ALWAYS do this in the opposite order. Further, I've only noticed this in the past few years. I've been programming in C for over 25 years and I've not seen this until, say, about the last 4 years or so. So my question is:

Is there a reason people are doing this and if so what is it? Is this a common standard in some languages, or projects, or is it taught in some universities? or is that just a few people trying to be different?

回答1:

This is called "Yoda-Style" (or "Yoda conditions" or "Yoda notation") and should prevent you from accidentally writing

if (bar = MY_CONSTANT) {
    /*  then do something */
}

since

if (MY_CONSTANT = bar) {
    /*  then do something */
}

would trigger a compiler error.

The name is derived from the uncommon twisted sentence construction the Star Wars character Yoda is also using.

In my opinion using "Yoda-Style" makes understanding of code harder because it is against the normal sentence construction rules. Also code quality checker (or as mentioned in the comments maybe even the compiler itself) should complain about such assignments anyway, so that (imho) there is no good reason to obfuscate your code.

回答2:

This is something of a best practice which someone thought best 15 years ago or so. Alleged benefit was that it would prevent someone from doing accidental assignments instead of comparison.

It was dubious back than, it is 100% moot nowadays since any compiler worth using will warn about assignment in branch operator, but hordes of lemmings still copy best practice without even thinking what it means or what it is for.

来源：https://stackoverflow.com/questions/36723200/coding-style-of-if-statements

标签

coding-style