CODEWITHSUNDEEP
language-agnosticnull
M Rajoy
M Rajoy

Reputation: 4094

null == object instead of object == null

I've seen this in a few places, people using 

if(null == myInstance)

instead of 

if(myInstance == null)

Is the former just a matter of style or does it have any performance impact in front of the (more intuitive, in my opinion) latter?

Upvotes: 1

Views: 66

Answers (2)

Vlad
Vlad

Reputation: 35594

It depends actually on the language you are using.

In the languages where only bool type is recognized as a condition inside if, if (myinstance == null) is preferred as it reads more naturally.

In the languages where other types can be treated (implicitly casted, etc.) as a condition the form if (null == myinstance) is usually preferred. Consider, for example, C. In C, ints and pointers are valid inside if. Additionally, assignment is treated as an expression. So if one mistakenly writes if (myinstance = NULL), this won't be detected by the compiler as an error. This is known to be a popular source of bugs, so the less readable but more reliable variant is recommended. Actually, some modern compilers issue a warning in case of assignment inside if (while, etc.), but not an error: after all, it's a valid expression in C.

Upvotes: 5

Ben-G
Ben-G

Reputation: 5026

You do that, to avoid that you by mistake set the value of myInstance to null.

Example for a typo:

if (null = myConstant) // no problem here, just won't compile


if (myConstant = null) // not good. Will compile anyway.

In general a lot of developers will put the constant part of the equation in first position for that reason.

Writing conditional checks this way is also referred to as Yoda Conditions.

Upvotes: 1

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