Nspredicate usage, array de-weight, comparison ...

Generally this is quite a lot, for example, you read a array1 from a file, and then you want to filter out an element in the program that conforms to the content in Array1. Array2.

1) Example one, a loop

Nsarray *arrayfilter = [Nsarray arraywithobjects:@ "pict", @ "Blackrain", @ "IP", nil];

Nsarray *arraycontents = [Nsarray arraywithobjects:@ "I am a picture." @ "I'm a guy" @ "I am Gagaga" @ "ipad" @ "iphone", NIL];

I want to filter arraycontents, just loop arrayfilter.

int i = 0, count = [Arrayfilter count];

for (i = 0; i < count; i + +)

{

NSString *arrayitem = (NSString *) [Arrayfilter objectatindex:i];

Nspredicate *filterpredicate = [[Nspredicate predicatewithformat:@ "Self CONTAINS%@", Arrayitem];

NSLog (@ "Filtered array with filter%@,%@", Arrayitem, [arraycontents filteredarrayusingpredicate:filterpredicate]);

}

Of course the above code arraycontent best use mutable, so you can directly filter, Nsarray is not modifiable.

2) Example Two, no loop required

Nsarray *arrayfilter = [Nsarray arraywithobjects:@ "ABC1", @ "ABC2", nil];

Nsarray *arraycontent = [Nsarray arraywithobjects:@ "A1", @ "ABC1", @ "ABC4", @ "ABC2", nil];

Nspredicate *thepredicate = [nspredicate predicatewithformat:@ ' not ' (self in%@) ", Arrayfilter];

[Arraycontent Filterusingpredicate:thepredicate];

So arraycontent filter out is not to include all the item in the Arrayfilter.

3) Generate file path under File collection list

Nsfilemanager *filemanager = [Nsfilemanager Defaultmanager];
NSString *defaultpath = [[NSBundle mainbundle] resourcepath];
Nserror *error;
Nsarray *directorycontents = [FileManager contentsofdirectoryatpath:defaultpath error:&error]

4) Usage of match

1. Simple comparison

NSString *match = @ "Imagexyz-999.png";
Nspredicate *predicate = [Nspredicate predicatewithformat:@ "self = =%@", match];
Nsarray *results = [directorycontents filteredarrayusingpredicate:predicate];

2. Usage of the like in match (similar to the usage in SQL)
NSString *match = @ "Imagexyz*.png";

Nspredicate *predicate = [Nspredicate predicatewithformat:@ "Self like%@", match];

Nsarray *results = [directorycontents filteredarrayusingpredicate:predicate];

3. Case comparison
[c] means ignoring the case, [d] means ignoring the accent and can be used together as follows:
NSString *match = @ "Imagexyz*.png";

Nspredicate *predicate = [Nspredicate predicatewithformat:@ "self like[cd]%@", match];

Nsarray *results = [directorycontents filteredarrayusingpredicate:predicate];

4. Using the regular

NSString *match = @ "Imagexyz-\\d{3}\\.png"; Imagexyz-123.png

Nspredicate *predicate = [Nspredicate predicatewithformat:@ "self matches%@", match];

Nsarray *results = [directorycontents filteredarrayusingpredicate:predicate];

Summarize:

1) When using an operator of an aggregate class, it is not necessary to loop the

2) when using an operator of a single comparison class, you can take a loop to get it done

PS, example one tries to use [@ "Self CONTAINS%@", Arrayfilter] to filter will hang, because CONTAINS when the string comparison operator, not the set operator.

The usage of nspredicate http://www.cnblogs.com/MarsGG/articles/1949239.html

Nspredicate usage, array de-weight, comparison ...