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POobjective-c Parameters not passes properly
 

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  1. POobjective-c Parameters not passes properly
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    <p>I have the following code:</p> <pre><code>[self swap:set :begin :begin+i]; //swap </code></pre> <p>calling the following swap method:</p> <pre><code>-(void) swap:(NSMutableString *)set:(NSInteger)first:(NSInteger)second { NSRange rangeSecond = NSMakeRange((NSUInteger) second, 1); NSRange rangeFirst = NSMakeRange((NSUInteger) first, 1); NSString *chsecond = [set substringWithRange:rangeSecond ]; [set replaceCharactersInRange:rangeSecond withString:[set substringWithRange:rangeFirst]]; [set replaceCharactersInRange:rangeFirst withString:chsecond]; } </code></pre> <p>The very first time this swap routine is called, it crashes at the statement:</p> <pre><code>[set replaceCharactersInRange:rangeSecond withString:[set substringWithRange:rangeFirst]]; </code></pre> <p>without leaving any debug information. Before calling swap I can hover over set, begin and i and they all have valid values. After swap is called when I hover over "first" it says (data variable, no debug info)first (unknown type)</p> <p>This program was working fine and this happened suddenly. Any idea why this is happening? Thanks</p> <p>Here is the whole chain of calls. start StartPermutate calls permute which calls swap. Is there any problems in the way I pass the parameters?</p> <pre><code>-(void) permute: (NSMutableString *) set :(NSInteger ) begin :(NSInteger ) end { int i; int range = end - begin; if(range == 1) { if([self is_word_valid:set]) { [self addWord:selectedWords : set]; } } else { for(i=0; i&lt;range; i++) { NSLog(@"set = '%@', first = '%@', second = '%@'", set, begin, begin + i); [self swap:set :begin :begin+i]; //swap [self permute:set :begin+1 :end]; // recursion [self swap:set :begin :begin+i]; // swap back } } } -(NSMutableArray *)StartPermutate: (NSMutableString *) letters { [self permute:letters :0 :(NSInteger)[letters length]]; return selectedWords; } </code></pre>
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    1. COThat method name is really horrible. Also, what are your code trying to do? Please describe in words what you are trying to do. Then people can more easily find logical errors if your code.
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      1. USDavid Rönnqvist
    2. COThe code in swap simply swaps two characters located at position "first" and "second". But the real problem may be the value is not passed to "first" in swap as I explained.
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    3. COUse NSLog to print your string, string length, and the two position values on entry to the method.
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      1. USHot Licks
 

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