Go exceed API source code reading (IV) -- save (), SaveAs (name string)

Go-Excelize API Source code reading （ Four ）——Save()

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One 、Go-Excelize brief introduction

Excelize yes Go Language written for operation Office Excel Document base library , be based on ECMA-376,ISO/IEC 29500 international standard . You can use it to read 、 Written by Microsoft Excel 2007 Spreadsheet documents created by and above . Support XLAM / XLSM / XLSX / XLTM / XLTX And so on , Highly compatible with styles 、 picture ( surface )、 PivotTable 、 Slicer and other complex components of the document , And provide streaming reading and writing API, For workbooks that contain large amounts of data . It can be applied to various report platforms 、 Cloud computing 、 Edge computing and other systems . Required to use this class library Go The language is 1.15 Or later .

Two 、Save()

func (f *File) Save() error
Use Save Save pairs Excel Editing of documents .

func (f *File) Save() error {
    
	if f.Path == "" {
    
		return ErrSave
	}
	if f.options != nil {
    
		return f.SaveAs(f.Path, *f.options)
	}
	return f.SaveAs(f.Path)
}

Save It can be used to overwrite the spreadsheet in the source path .
first if Judge , Is to judge whether the path to save is empty , If it is empty, return ErrSave.

	// ErrSave defined the error message for saving file.
	ErrSave = errors.New("no path defined for file, consider File.WriteTo or File.Write")

This item places errors in errors.go in .ErrSave Is the error message of an error when saving the file .

Next if Judge ：

	if f.options != nil {
    
		return f.SaveAs(f.Path, *f.options)
	}

When the file structure options When the member is not empty , Saving files requires consideration options Information about .
If it is empty, there is no need to consider .

3、 ... and 、SaveAs(name string)

as for SaveAs(name string), Let's see ：
Use SaveAs preservation Excel The document is the specified file .

func (f *File) SaveAs(name string, opt ...Options) error {
    
	if len(name) > MaxFilePathLength {
    
		return ErrMaxFilePathLength
	}
	f.Path = name
	contentType, ok := map[string]string{
    
		".xlam": ContentTypeAddinMacro,
		".xlsm": ContentTypeMacro,
		".xlsx": ContentTypeSheetML,
		".xltm": ContentTypeTemplateMacro,
		".xltx": ContentTypeTemplate,
	}[filepath.Ext(f.Path)]
	if !ok {
    
		return ErrWorkbookFileFormat
	}
	f.setContentTypePartProjectExtensions(contentType)
	file, err := os.OpenFile(filepath.Clean(name), os.O_WRONLY|os.O_TRUNC|os.O_CREATE, os.ModePerm)
	if err != nil {
    
		return err
	}
	defer file.Close()
	f.options = nil
	for i := range opt {
    
		f.options = &opt[i]
	}
	return f.Write(file)
}

first if:

	if len(name) > MaxFilePathLength {
    
		return ErrMaxFilePathLength
	}

Used to judge whether the length of the file name is legal .

The file error message is as follows ：

Next, determine the content type according to the file extension ：

	contentType, ok := map[string]string{
    
		".xlam": ContentTypeAddinMacro,
		".xlsm": ContentTypeMacro,
		".xlsx": ContentTypeSheetML,
		".xltm": ContentTypeTemplateMacro,
		".xltx": ContentTypeTemplate,
	}[filepath.Ext(f.Path)]

The writing method of this paragraph can be learned ... As for its content, the following figure can be seen ...

setContentTypePartProjectExtensions() Will get contentType Assign to document relation part and main document part .
Then open the file and write f File stream .

os.O_WRONLY|os.O_TRUNC|os.O_CREATE, os.ModePerm
I want to introduce this ：

os.O_APPEND： When writing to a file , Append new content to existing content .
os.O_CREATE： When the file on the given path does not exist , Create a new file .
os.O_EXCL： Need and os.O_CREATE Use together , Indicates that there cannot be an existing file on the given path .
os.O_SYNC： Synchronize on open files I/O. It ensures that the contents read and written are always synchronized with the data on the hard disk .
os.O_TRUNC： If the file already exists , And it's a regular file , Then empty anything that already exists .

os.O_WRONLY | os.O_CREATE | O_EXCL 【 If it already exists , The failure 】
os.O_WRONLY | os.O_CREATE 【 If it already exists , Will cover up and write , Will not empty the original file , It's all over the top 】
os.O_WRONLY | os.O_CREATE | os.O_APPEND 【 If it already exists , Then add at the end 】