Objective c should i use nonatomic

So, would you want a synchronization primitive such as a spin lock or mutex implicitly surrounding every get and set, knowing it does not guarantee thread safety? I certainly don't! Making every property access in your implementations atomic can consume a ton of CPU time. Implementation Detail: some accesses do not require spin locks to uphold guarantees of atomic ; it depends on several things, such as the architecture and the size of a variable.

So to answer your question "any side-effect? If you use performSelectorInBackground:withObject: to spawn a new thread, then the performed selector is responsible for setting up the new thread's autorelease pool, run loop and other configuration details — see "Using NSObject to Spawn a Thread" in Apple's Threading Programming Guide. Updated with a hat tip to Chris Nolet, who suggested a change that makes the above code simpler and keeps up with Apple's latest GCD code examples.

Prior to some version of the compiler that I don't remember the synthesis statement didn't create the ivar. Instead it only said what variable it should use so you had to declare both the variable and the property.

If you synthesized with a underscore prefix then your variable needed to have the same prefix. Now you don't have to create the variable yourself anymore, instead a variable with the variableName that you specified in the synthesis statement will be created if you didn't already declare it yourself in which case it is just used as the backing variable of the property. These are not the same variable so changing one of them changes nothing about the other.

Some people feel that the code becomes cleaner if you don't have to write self. People also say that it is faster since it doesn't require a method call though it is probably never ever going to have a measurable effect on your apps performance.

Accepted Answer. Posted by SevenTenEleven. Post marked as solved. I assume the reference types properties in Swift are nonatomic. Posted by tompelaia2. Appledoc says the following:. I never had a problem using atomic at all. I designed the code that way, that there is not problem with atomic properties. In answer to your third paragraph; essentially yes. An atomic number can't be read while a thread is writing the number.

No setter and getter methods will be synthesized. If you need to specify multiple attributes, simply include them as a comma-separated list, like this:. Variable property attributes or Modifiers in iOS. Suppose there is an atomic string property called "name", and if you call [self setName: "A"] from thread A, call [self setName: "B"] from thread B, and call [self name] from thread C, then all operation on different thread will be performed serially which means if one thread is executing setter or getter, then other threads will wait.

Developer should ensure thread safety for such objects. If the property "name" was nonatomic, then all threads in above example - A,B, C and D will execute simultaneously producing any unpredictable result. Imagine our object is a dog, and that the dog wants to run away be deallocated.

Strong pointers are like a leash on the dog. As long as you have the leash attached to the dog, the dog will not run away.

If five people attach their leash to one dog, five strong pointers to one object , then the dog will not run away until all five leashes are detached. Weak pointers, on the other hand, are like little kids pointing at the dog and saying "Look!