PHP会话变量(php session variable)

 我不完全确定你要做什么，但如果你想节省一些打字，你为什么不这样做： 
 
// assign the label you want to use to a local variable

UILabel *selectedLabel;
selectedLabel = nil;
if (is_x) {
    selectedLabel = labelField_x;
} else if (is_y) {
    selectedLabel = labelField_y;
} else if (is_z) {
    selectedLabel = labelField_z;
}

// now work with selectedLabel so you don't have to repeat yourself

if (!pressedDecimal){
    selectedLabel.text = ...
 
 或者您甚至可以将IBOutlet属性中的标签粘贴到字典中，以便快速为任何给定字符（字符串）获取正确的标签： 
 
// create a lookup dictionary (once, e.g. in awakeFromNib)

NSDictionary *labelForCharacter;
labelForCharacter = @{
    @"x" : labelField_x,
    @"y" : labelField_y,
    @"z" : labelField_z
};

 // get the label for "z"

UILabel *selectedLabel;
selectedLabel = labelForCharacter[@"z"];

I'm not entirely sure what you're up to, but if you want to save yourself some typing, why don't you do something like this:
 
// assign the label you want to use to a local variable

UILabel *selectedLabel;
selectedLabel = nil;
if (is_x) {
    selectedLabel = labelField_x;
} else if (is_y) {
    selectedLabel = labelField_y;
} else if (is_z) {
    selectedLabel = labelField_z;
}

// now work with selectedLabel so you don't have to repeat yourself

if (!pressedDecimal){
    selectedLabel.text = ...
 
Or you could even stick the labels from your IBOutlet properties right into a dictionary so you can quickly get the right label for any given character (string):
 
// create a lookup dictionary (once, e.g. in awakeFromNib)

NSDictionary *labelForCharacter;
labelForCharacter = @{
    @"x" : labelField_x,
    @"y" : labelField_y,
    @"z" : labelField_z
};

 // get the label for "z"

UILabel *selectedLabel;
selectedLabel = labelForCharacter[@"z"];