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iOS user info in NSTimer
- Thread starter grandM
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userInfo is for the user to decide. The user in this case is the developer. An example might be a timer that's meant to go off at a set of times that are not regular, say 1 sec, then 4 secs, then 10 secs. The userInfo could be an array holding those times and each time the timer goes off it sets the next time to go off from the list. When the timer is first created the array is created and the userInfo is set to the timer. Then the array could have one value removed. Then a new timer is created with the new array. And so on.
In most cases there are other ways to accomplish things that the userInfo might be used for but sometimes it's the most convenient way. It's kind of like the userInfo in NSNotification and NSError. Use it for whatever you want.
In most cases there are other ways to accomplish things that the userInfo might be used for but sometimes it's the most convenient way. It's kind of like the userInfo in NSNotification and NSError. Use it for whatever you want.
So if you initialize a Timer object myTime and you add as a parameter [1.0, 4.0, 10.0] it will fire at the first, fourth and tenth second? Why is the creation of a new Timer object required then?
User info is just a way to pass information to the timer callback function (for instance, the object creating the timer, or a sound, or anything known at the time of creating the timer, but possibly not at other times). The information must be in the form of an Objective C object (perhaps encapsulating lots of other information).
@gramdM, my example was just an example. There is no automatic firing of timers at staggered intervals. If you want that you could use my example description to do that.
OK, another, maybe simpler example. You want an image to appear in an image view after a delay. Or you want a sound to play, after a delay. You create the timer object and set the userInfo property to be the UIImage or Sound object to be used. Then when the timer fires the timer callback method reads the userInfo and casts it to the appropriate type and then uses it, to show the image or play the sound.
OK, another, maybe simpler example. You want an image to appear in an image view after a delay. Or you want a sound to play, after a delay. You create the timer object and set the userInfo property to be the UIImage or Sound object to be used. Then when the timer fires the timer callback method reads the userInfo and casts it to the appropriate type and then uses it, to show the image or play the sound.
The userInfo property of the timer can be used and abused however you like. Basically it exists for people who are reluctant to use global scope variables but want to persist some value/object for some period of time.
It's especially useful when you have two separate timers that trigger/act upon the same function to accomplish different tasks. Thus, the timer function will exhibit either completely or partially different behavior depending on what was passed in via user info.
It's especially useful when you have two separate timers that trigger/act upon the same function to accomplish different tasks. Thus, the timer function will exhibit either completely or partially different behavior depending on what was passed in via user info.
No. Creating an example should be an exercise for the student. Come back if there are bugs in your attempt.