style sheet problem

I wrote code like:

+ (CGFloat)tableView:(UITableView*)tableView rowHeightForObject:(id)item {
    CustomTTTableSubtitleItem* captionedItem = item;
    CGFloat maxWidth = tableView.width - kHPadding*2;
    CGSize titleSize = [captionedItem.title sizeWithFo开发者_如何学Gont:TTSTYLEVAR(myTitleFont) constrainedToSize:CGSizeMake(maxWidth, CGFLOAT_MAX) lineBreakMode:UILineBreakModeWordWrap];
}

Got this exception:

2011-07-24 03:10:18.762 xinyou[15941:b303] -[TTDefaultStyleSheet myTitleFont]: unrecognized selector sent to instance 0x5b5e120 2011-07-24 03:10:18.765 xinyou[15941:b303] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[TTDefaultStyleSheet myTitleFont]: unrecognized selector sent to instance 0x5b5e120' * Call stack at first throw: ( 0 CoreFoundation

0x0119a5a9 exceptionPreprocess + 185 1 libobjc.A.dylib

0x012ee313 objc_exception_throw + 44 2 CoreFoundation

0x0119c0bb -[NSObject(NSObject) doesNotRecognizeSelector:] + 187 3

CoreFoundation 0x0110b966 __forwarding + 966 4 CoreFoundation 0x0110b522 _CF_forwarding_prep_0 + 50 5 xinyou

0x000081f9 +[CustomTTTableSubtitleItemCell tableView:rowHeightForObject:] + 186 6 xinyou

0x000a6c92 -[TTTableViewVarHeightDelegate tableView:heightForRowAtIndexPath:] + 156 7 UIKit

0x0064a6d5 -[UISectionRowData

In this exception you can see [TTDefaultStyleSheet myTitleFont]: unrecognized selector sent to instance 0x5b5e120 but actually myTitleFont defined in XYDefaultStyleSheet and I've imported XYDefaultStyleSheet.h in my class. XYDefaultStyleSheet.h and XYDefaultStyleSheet.m are like:

XYDefaultStyleSheet.h

#import "Three20/Three20.h"

@interface XYDefaultStyleSheet : TTDefaultStyleSheet

@property(nonatomic,readonly) UIColor* myHeadingColor;
@property(nonatomic,readonly) UIColor* mySubtextColor;
@property(nonatomic,readonly) UIColor* myTitleColor;
@property(nonatomic,readonly) UIFont* myTitleFont;
@property(nonatomic,readonly) UIFont* myHeadingFont;
@property(nonatomic,readonly) UIFont* mySubtextFont;


@end

XYDefaultStyleSheet.m

#import "XYDefaultStyleSheet.h"


///////////////////////////////////////////////////////////////////////////////////////////////////

@implementation XYDefaultStyleSheet


///////////////////////////////////////////////////////////////////////////////////////////////////
// styles

///////////////////////////////////////////////////////////////////////////////////////////////////
// public colors

- (UIColor*)myTitleColor {
    return [UIColor blackColor];
}

- (UIColor*)myHeadingColor {
    return RGBCOLOR(80, 110, 140);
}

- (UIColor*)mySubtextColor {
    return [UIColor grayColor];
}


///////////////////////////////////////////////////////////////////////////////////////////////////
// public fonts

- (UIFont*)myTitleFont {
    return [UIFont boldSystemFontOfSize:16];
}

- (UIFont*)myHeadingFont {
    return [UIFont boldSystemFontOfSize:13];
}

- (UIFont*)mySubtextFont {
    return [UIFont systemFontOfSize:12];
}


@end

why always tell [TTDefaultStyleSheet myTitleFont] ... if the problem is really myTitleFont, it should be [XYDefaultStyleSheet myTitleFont], why TTDefaultStyleSheet?

got it! Init my style sheet in AppDelegate.

This is an answer to @Jason Zhao's answer about initialising within the AppDelegate.

- (void)applicationDidFinishLaunching:(UIApplication *)application {      
    // Override point for customization after app launch   
    [TTStyleSheet setGlobalStyleSheet:[[[CustomDefaultStyleSheet alloc]  
                                        init] autorelease]];  

    [window addSubview:[navigationController view]];  
    [window makeKeyAndVisible];  
}  

Original code is from here, which has a lot of useful information about using TTStyleSheet's:

Three20 Stylesheets iPhone Tutorial