The Magical magic of Valueforkeypath (turn)

Probably everyone to -(ID) Valueforkeypath: (NSString *) KeyPath method is not very understanding.

In fact, this method is very powerful, for example:

Nsarray *array = @[@"name"@ "w"@ "aa"  @ "jimsa"]; NSLog (@ "%@", [array Valueforkeypath:@ "uppercasestring  "]); output (    NAME,    W,    AA,    Jimsa)

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The equivalent of each member of the array uppercaseString executes the method and then returns the returned object as a new array.

Since the method uppercaseString can be used, then other methods of NSString , such as

[Array Valueforkeypath:@ "length"]

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Returns an array of the components of each string length. As long as you can think of the member instance method can be so used.

If you think this method is a bit of a function, it's wrong. Let's take a concrete example and keep looking down.

RightNSNumberAn array calculates the sum, mean, maximum, minimum of an array quickly

Nsarray *array = @[@1, @2, @3, @4, @Ten]; NSNumber*sum = [Array Valueforkeypath:@"@sum. Self"]; NSNumber*avg = [Array Valueforkeypath:@"@avg. Self"]; NSNumber*max = [Array Valueforkeypath:@"@max. Self"]; NSNumber*min = [Array Valueforkeypath:@"@min. Self"];

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Or specify the output type

 1  nsnumber *sum = [array valueforkeypath:@ "   @sum. Floatvalue   " ]; 2  nsnumber *avg = [array valueforkeypath:@ "   @avg. Floatvalue   " ]; 3  nsnumber *max = [array valueforkeypath:@ "   @max. Floatvalue   " ]; 4  nsnumber *min = [array valueforkeypath:@ "   @min. Floatvalue   "]; 

View CodeEliminate duplicate data

1Nsarray *array = @[@"name",@"W",@"AA",@"Jimsa",@"AA"];2NSLog (@"%@", [array Valueforkeypath:@"@distinctUnionOfObjects. Self"]);

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1 Print 2 3 (4name,5W,6Jimsa,7AA 8 )

View CodeRight nsdictionaryArray to quickly find the corresponding KeyThe value of the pair

1Nsarray *array = @[@{@"name":@"cookeee",@"Code": @1},2@{@"name":@"Jim",@"Code": @2},3@{@"name":@"Jim",@"Code": @1},4@{@"name":@"Jbos",@"Code": @1}];5NSLog (@"%@", [array Valueforkeypath:@"name"]);

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An array of values directly from the name key in the dictionary, which is obviously easier to add to the new array than the loop value

1 (2    cookeee,3    Jim,4    Jim,  5    jbos6 )

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Also can be nested use, first eliminate name the corresponding value of the duplicate data and then take the value

1Nsarray *array = @[@{@"name":@"cookeee",@"Code": @1},2@{@"name":@"Jim",@"Code": @2},3@{@"name":@"Jim",@"Code": @1},4@{@"name":@"Jbos",@"Code": @1}];5 6NSLog (@"%@", [array Valueforkeypath:@"@distinctUnionOfObjects. Name"]);7 8 Print9 (Ten Cookeee, One Jim, A Jbos -)

View CodeChangeUitextfiedlOf placeholderThe color

1     [Searchfield Setvalue:[uicolor Whitecolor] Forkeypath:@ "_placeholderlabel.textcolor" ];

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It's a - (void)drawPlaceholderInRect:(CGRect)rect; lot easier than rewriting.

Go to: http://segmentfault.com/a/1190000000526660

The Magical magic of Valueforkeypath (turn)