110 lines
3.1 KiB
Markdown
110 lines
3.1 KiB
Markdown
Read an JSON content {#ejson_tutorial_read}
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===================
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@tableofcontents
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The first thing to do when reading or writing a JSON file/stream, is to declare the Document interface
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Include ejson
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@snippet read.cpp ejson_sample_include
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Declare document interface
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@snippet read.cpp ejson_sample_declare_doc
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Read an JSON file {#ejson_tutorial_read_file}
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================
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File to read: "read.json"
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@include read.json
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Reading a file is done like this:
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@snippet read.cpp ejson_sample_read_file
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The file naming is manage by @ref etk::FSNode that provide "DATA:///" start string for internal application asset. You can use external path like "./plop/file.json" too.
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Read an JSON Stream {#ejson_tutorial_read_stream}
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==================
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Reading a stream is done like this:
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@snippet read.cpp ejson_sample_read_stream1
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In C and C++ it is very hard to read string with the \\" then to simplify parsing of json the parser engine support the use of simple **'** interface:
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@snippet read.cpp ejson_sample_read_stream2
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Access at all Element datas {#ejson_tutorial_read_folow}
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===========================
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In an ejson::Object (or ejson::Document) the sub-nodes are accessible threw an abstraction class stores in an element name **Value**
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Get a value with its name:
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@snippet read.cpp ejson_sample_read_get_element
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Access to a string in an Object:
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-------------------------------
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The generic Way to access to an element is to convert it in the corect type:
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@snippet read.cpp ejson_sample_read_convert_string
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Commonly you might use like this:
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@snippet read.cpp ejson_sample_read_get_string
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Access to a boolean in an Object:
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---------------------------------
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@snippet read.cpp ejson_sample_read_get_boolean
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Access to a Number in an Object:
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---------------------------------
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By default a number is a double (herited from the js internal property)
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@snippet read.cpp ejson_sample_read_get_number
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But it is possible to read large number directly in 64 bits mode (better for entier number, no round generated.)
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@snippet read.cpp ejson_sample_read_get_number_64_bits
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Access to a Array in an Object:
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---------------------------------
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Get the Array
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@snippet read.cpp ejson_sample_read_get_array
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Move threw all element:
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@snippet read.cpp ejson_sample_read_move_threw_array
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Move threw all element in C mode:
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@snippet read.cpp ejson_sample_read_move_threw_array_c
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Access to a Object in an Object:
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---------------------------------
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Get the Object
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@snippet read.cpp ejson_sample_read_get_object
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Move threw all element:
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@snippet read.cpp ejson_sample_read_move_threw_object
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Move threw all element in C mode:
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@snippet read.cpp ejson_sample_read_move_threw_object_c
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Now we can copy the Object we want
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==================================
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ejson manage reference object, then it is possible that 2 part of the software access at the same object/element ...
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You can copy object to separate or duplicate section.
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This is named cloning:
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@snippet read.cpp ejson_sample_read_clone
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All example file {#ejson_tutorial_read_all}
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================
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@include read.cpp
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