Returns a description of the format exception.
The description always contains the message.
If source is present and is a string, the description will contain (at least a part of) the source. If offset is also provided, the part of the source included will contain that offset, and the offset will be marked.
If the source is a string and it contains a line break before offset, only the line containing offset will be included, and its line number will also be part of the description. Line and character offsets are 1-based.
String toString() { String report = "FormatException"; if (message != null && "" != message) { report = "$report: $message"; } int offset = this.offset; if (source is! String) { if (offset != null) { report += " (at offset $offset)"; } return report; } if (offset != null && (offset < 0 || offset > source.length)) { offset = null; } // Source is string and offset is null or valid. if (offset == null) { String source = this.source; if (source.length > 78) { source = source.substring(0, 75) + "..."; } return "$report\n$source"; } int lineNum = 1; int lineStart = 0; bool previousCharWasCR = false; for (int i = 0; i < offset; i++) { int char = source.codeUnitAt(i); if (char == 0x0a) { if (lineStart != i || !previousCharWasCR) { lineNum++; } lineStart = i + 1; previousCharWasCR = false; } else if (char == 0x0d) { lineNum++; lineStart = i + 1; previousCharWasCR = true; } } if (lineNum > 1) { report += " (at line $lineNum, character ${offset - lineStart + 1})\n"; } else { report += " (at character ${offset + 1})\n"; } int lineEnd = source.length; for (int i = offset; i < source.length; i++) { int char = source.codeUnitAt(i); if (char == 0x0a || char == 0x0d) { lineEnd = i; break; } } int length = lineEnd - lineStart; int start = lineStart; int end = lineEnd; String prefix = ""; String postfix = ""; if (length > 78) { // Can't show entire line. Try to anchor at the nearest end, if // one is within reach. int index = offset - lineStart; if (index < 75) { end = start + 75; postfix = "..."; } else if (end - offset < 75) { start = end - 75; prefix = "..."; } else { // Neither end is near, just pick an area around the offset. start = offset - 36; end = offset + 36; prefix = postfix = "..."; } } String slice = source.substring(start, end); int markOffset = offset - start + prefix.length; return "$report$prefix$slice$postfix\n${" " * markOffset}^\n"; }
© 2012 the Dart project authors
Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
https://api.dartlang.org/stable/2.0.0/dart-core/FormatException/toString.html