iOS Interview Questions And Answers For 1-2 years Experienced Candidates.

1.How do I convert NSMutableArray to NSArray?

Answer:

In this post I have explained some key functionalities of NSArray and NSMutableArray.

I would like to elaborate some possible solutions with explanation.

1)NSArray *array = [NSArray arrayWithArray:mutableArray];
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Note:
What if the NSMutableArray is nil ?

NSMutableArray *mutableArray = nil;
NSArray *array = [NSArray arrayWithArray:mutableArray];

In the above case,the array is returned as an empty array.
​
(array == @[] )

For Example:-

 (Which is an empty array but not nil).

2)NSArray *array = [mutableArray copy];

Note:
What if the NSMutableArray is nil ?

NSMutableArray *mutableArray = nil;
NSArray *array = [mutableArray copy];
The above code returns array as nil. (array==nil)

3)
NSArray *array = [[NSArray alloc] initWithArray:mutableArray];

It returns an array which is not autoreleased.

Note:

NSArray *array = [NSArray arrayWithArray:mutableArray];

It returns an array which is autoreleased.

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2.How to convert an NSArray to String in Objective-C ?
Answer:-

NSArray  *array1 = [NSArray arrayWithObjects:@"a", @"b", @"c", nil];
NSString *StringVal = [array1 componentsJoinedByString:@","];

It returns a String with value "abc".

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3.How to convert an NSMutableArray to String in Objective-C ?
Answer:-

MArray = [[NSMutableArray alloc] init];
[MArray addObject:@"ABCD"];
[MArray addObject:@"EFGH"];
NSString *StringVal=[MArray description];
                                  OR
NSString *StringVal=[MArray componentsJoinedByString:@", "];

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4.How to sort an NSMutableArray with custom objects in it?
Answer:-

We can easily sort an array using Blocks.

NSArray *MySortedarray;
MySortedarray = [BillDetails sortedArrayUsingComparator:^NSComparisonResult(id a, id b) {    NSDate *first = [(Person*)a birthDate];
NSDate *second = [(Person*)b birthDate];
 return [first compare:second];
}];

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5.How can I fill an NSMutableArray dynamically?
Answer:-

int count = [CArray count];
NSMutableArray *resultArray = [[NSMutableArray alloc] initWithCapacity:count];
for (NSString  *name in CArray) {
 UIImage *image = [UIImage imageNamed:name]; 
 [resultArray addObject: image];
}

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6.How to replace content of NSMutableArray with NSArray ?
Answer:

DataArray = [resultArray mutableCopy];

In the above example, DataArray is NSMutableArray and resultArray is NSArray.
OR
NSMutableArray *DataArray = [[NSMutableArray alloc] initWithContentsOfArray:resultArray];

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