Issue in UITextView beginningOfDocument in iOS 4.3 - iphone

Question

Below is the code which I am using and working fine in simulator iOS 5+, but giving issue in simulator 4.3
UITextPosition *begin = [self.tvQuestion positionFromPosition:self.tvQuestion.beginningOfDocument offset:nrange.location];
Following is the error statement:
Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UITextView beginningOfDocument]: unrecognized selector sent to instance 0x5586050'
Could somebody advice on this? Thanks in advance!

Answer 1

The UITextInput protocol includes a beginningOfDocument selector since iOS 3.2.
But UITextView only adopted UITextInput since iOS 5.0. It was previously conforming to the UITextInputTraits protocol.
Source: search for UITextView here http://developer.apple.com/library/ios/#releasenotes/General/iOS50APIDiff/index.html
If you want it to work on iOS 4.x and later, you have to perform a check and do the computation by yourself on iOS 4:
CGRect newRect = CGRectZero;
if ([UITextView conformsToProtocol:#protocol(UITextInput)]) {
// iOS 5 and later
UITextPosition *begin = [self.tvQuestion positionFromPosition:self.tvQuestion.beginningOfDocument offset:nrange.location];
UITextPosition *end = [self.tvQuestion positionFromPosition:begin offset:nrange.length];
UITextRange *textRange = [self.tvQuestion textRangeFromPosition:begin toPosition:end];
newRect = [self.tvQuestion firstRectForRange:textRange];
} else {
// iOS 3.2 to 4.3
// Compute text position manually
#define TEXT_VIEW_PADDING 8.f
NSString *textContent = [self.tvQuestion.text substringToIndex:NSMaxRange(nrange)];
NSDictionary *ctFontDescriptorAttributes = [NSDictionary dictionaryWithObjectsAndKeys:
self.tvQuestion.font.familyName, kCTFontFamilyNameAttribute,
// Uncomment for bold fonts
// [NSDictionary dictionaryWithObjectsAndKeys:
// [NSNumber numberWithInt:kCTFontBoldTrait], kCTFontSymbolicTrait,
// nil], kCTFontTraitsAttribute,
nil];
CTFontDescriptorRef ctFontDescriptor = CTFontDescriptorCreateWithAttributes((CFDictionaryRef)ctFontDescriptorAttributes);
CTFontRef ctFont = CTFontCreateWithFontDescriptor(ctFontDescriptor, self.tvQuestion.font.pointSize, NULL);
NSAttributedString *attributedText = [[NSAttributedString alloc] initWithString:textContent
attributes:[NSDictionary dictionaryWithObjectsAndKeys:
(id)ctFont, kCTFontAttributeName,
nil]];
CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)attributedText);
CFRange globalRange = CFRangeMake(0, [attributedText length]);
CGRect textRect = CGRectInset((CGRect){CGPointZero, self.tvQuestion.contentSize}, TEXT_VIEW_PADDING, TEXT_VIEW_PADDING);
CTFrameRef frame = CTFramesetterCreateFrame(framesetter, globalRange, CGPathCreateWithRect((CGRect){CGPointZero, textRect.size}, NULL), NULL);
CFArrayRef lines = CTFrameGetLines(frame);
NSInteger nbLines = CFArrayGetCount(lines);
CGPoint *lineOrigins = calloc(sizeof(CGPoint), nbLines);
CTFrameGetLineOrigins(frame, CFRangeMake(0, 0), lineOrigins);
CGFloat ascent = CTFontGetAscent(ctFont);
CGFloat descent = CTFontGetDescent(ctFont);
CGFloat leading = CTFontGetLeading(ctFont);
if (leading < 0) {
leading = 0;
}
leading = floor(leading + 0.5);
CGFloat lineHeight = floor(ascent + 0.5) + floor(descent + 0.5) + leading;
CGFloat firstLineYOffset = 0.f;
for (NSInteger i = 0; i < nbLines; i++) {
CTLineRef line = CFArrayGetValueAtIndex(lines, i);
CFRange lineRange = CTLineGetStringRange(line);
CGPoint lineOrigin = lineOrigins[i];
CGFloat ascent, descent, leading, width;
width = CTLineGetTypographicBounds(line, &ascent, &descent, &leading);
if (i == 0) {
firstLineYOffset = lineOrigin.y;
}
lineOrigin.y = (lineOrigin.y - firstLineYOffset) * -1.f;
if (nrange.location >= lineRange.location && nrange.location < lineRange.location + lineRange.length) {
CGFloat secOffset;
CGFloat startOffset = CTLineGetOffsetForStringIndex(line, nrange.location, &secOffset);
CGFloat rectWidth;
if (nrange.location + nrange.length <= lineRange.location + lineRange.length) {
CGFloat endOffset = CTLineGetOffsetForStringIndex(line, nrange.location + nrange.length, &secOffset);
rectWidth = endOffset - startOffset;
} else {
rectWidth = width - 5 - startOffset;
}
newRect = (CGRect)
{
{
lineOrigin.x + TEXT_VIEW_PADDING + startOffset,
lineOrigin.y + TEXT_VIEW_PADDING + i
}, {
rectWidth,
lineHeight
}
};
break;
}
}
free(lineOrigins);
CFRelease(frame);
CFRelease(framesetter);
CFRelease(ctFont);
CFRelease(ctFontDescriptor);
}

Answer 2

Although UITextView does not conform to UITextInput protocol on iOS 4.x, its subviews does. The following code works iOS 4.x and later.
UIView<UITextInput> *t = [textView.subviews objectAtIndex:0];
assert([t conformsToProtocol:#protocol(UITextInput)]);
// use t for the view conforming to UITextInput
UITextPosition *beginning = t.beginningOfDocument; // OK