iOS 數組使用 valueForKeyPath：計算求和、平均值、最大、最小

NSArray *testArray = [NSArray arrayWithObjects:@"2.0", @"2.3", @"3.0", @"4.0", nil];
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NSNumber *sum = [testArray valueForKeyPath:@"@sum.floatValue"];
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NSNumber *avg = [testArray valueForKeyPath:@"@avg.floatValue"];
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NSNumber *avg = [testArray valueForKeyPath:@"@max.floatValue"];
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NSNumber *avg = [testArray valueForKeyPath:@"@min.floatValue"];

如果是數據模型對象：比如數據模型對象有一個屬性 finishRate

CGFloat max = [[[self datas] valueForKeyPath:@"@max.finishRate"] floatValue];