Taxicab distance in ios app [closed] - ios

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Im making an ios game very similar to minesweeper in terms of layout and i have no clue how to do taxicab distance. Do I need to use core graphics or just an array or what?

See here .
In essence, the taxicab distance between (x1,y1) and (x2,y2) is |x1-x2| + |y1-y2| (|z| means abs(z))

My approach would have been to use a two-dimensional array - it just seems the simplest and most natural representation of the problem.
I would set all values of the array to 0, randomize and reset certain indices to -1 (mines), and increment the count of each adjacent square of these indices by 1.

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How to insert charactor like "don't" in Sqlite in ios [closed]

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I am inserting some keyword like Don't , has'nt in Sqlite which is not inserted.any one have idea about it.
Use ' as escape character and insert it like this:
dont''t
Documentation:
A single quote within the string can be encoded by putting two single quotes in a row - as in Pascal
In case you are using an API to connect with Sqlite, instead of manipulating the original string a better approach would be to use sqlite3_bind_text() function to bind a value to a ? placeholder in the SQL. Thanks to #Rob for pointing this out.

How does delete_at(n) work in Ruby? [closed]

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If I create a new array with 10 elements, and populate it with the numbers 1 through 10, then call delete_at(4), the fourth element is "deleted".
How does this work, though? Does it completely remove the element and index and reduce the size of the array to 9, or does it nullify (or make nil) the value of that index and push it the the end of the array?
It copies all of the elements after the position back one with a single memory copy, then reduces the size of the array by one.
Why do you ask? Are you trying to reason about performance?
Ref: https://github.com/ruby/ruby/blob/9f45081627cf682b3ee938353da134d6f28560da/array.c#L2964

Subtract Variable if Present in Ruby [closed]

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Given I have:
int1, int2, int3 = 1, nil, 3
how would I subtract these ints from another variable, only if they weren't nil? I can write something sloppy, but I want a single line process if possible.
another_variable - [int1, int2, int3].compact.sum
othervariable - int1.to_i # will turn nil into 0
You can write something like
ans = int1 && (int2-int1)

A calculator app on iOS [closed]

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Can anyone please explain the difference between this
[display setText:[[display text] stringByAppendingString:digit ]];
and this
[display setText:digit];
The code is rather clear. But if you don't understand:
Here [display setText:[[display text] stringByAppendingString:digit ]]; a new digit will be added to the digits currently displaying on the screen. This BOOL value userIsInTheMiddleOfTypingANumber is extremely straightforward - it is said that there are always digits on the screen and a new digit must be added to them. This method stringByAppendingString returns a new string made by appending a given digit to the currently displayed digits in the UITextField.
And here [display setText:digit]; all the text which are displayed in the UITextField will be overwritten with a new digit value. But as I suppose it is used when there are no digits on the screen and we need to write the first one.I don't know what is using for displaying digits in that app. But if it is UITextField then using setText is a bad idea - it is a deprecated method. You should use text property instead.
This is an extremely simple code which you need to understand yourself. So my advice you to read some introductory books on CocoaTouch and iOS with simple examples there are plenty of them: http://www.amazon.com/Beginning-iOS-Development-Exploring-SDK/dp/1430245123/ref=pd_sim_b_8 . And don't forget to use official documentation.

Limit a NSMutablestring's length [closed]

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I am working on a calculator App.
The NSMutablestring is used for calculation E.g "5-3*8-(-1)/77".
But the label can't display endless an NSMutablestring, so is there have any way to limit NSMutablestring's length?
(not too long, I want the NSMutablestring's length to be less than 100).
You can get the first 100 characters of a string as follows:
NSString *first100chars = [myString substringToIndex:100];
However, it sounds like you need to prevent the user from actually entering a string this long, which is a different problem. The comments to your question give examples of other people asking similar questions (e.g. Set the maximum character length of a UITextField), I suggest you check those.
This is a job for an NSFormatter subclass. That's exactly what it's for.

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