学步园

对于每一种类型进入到store的时候都会进行一次类型转换

如果字符串类型的，传递值转换失败，会检查默认值是否存在，字符串类型的默认值是空串

其次，如果没有指定使用null也会使用空串替换掉null

所以为了保持这个空串需要在Field上添加如下配置：

defaultValue : null,
useNull : true

源码如下

Ext.define('Ext.data.Types', {
    singleton: true,
    requires: ['Ext.data.SortTypes']
}, function() {
    var st = Ext.data.SortTypes;

    Ext.apply(Ext.data.Types, {
        /**
         * @property {RegExp} stripRe
         * A regular expression for stripping non-numeric characters from a numeric value. Defaults to <tt>/[\$,%]/g</tt>.
         * This should be overridden for localization.
         */
        stripRe: /[\$,%]/g,

        /**
         * @property {Object} AUTO
         * This data type means that no conversion is applied to the raw data before it is placed into a Record.
         */
        AUTO: {
            sortType: st.none,
            type: 'auto'
        },

        /**
         * @property {Object} STRING
         * This data type means that the raw data is converted into a String before it is placed into a Record.
         */
        STRING: {
            convert: function(v) {//这里的v就是默认值
                var defaultValue = this.useNull ? null : '';
                return (v === undefined || v === null) ? defaultValue : String(v);
            },
            sortType: st.asUCString,
            type: 'string'
        },

        /**
         * @property {Object} INT
         * This data type means that the raw data is converted into an integer before it is placed into a Record.
         * <p>The synonym <code>INTEGER</code> is equivalent.</p>
         */
        INT: {
            convert: function(v) {
                return v !== undefined && v !== null && v !== '' ?
                    parseInt(String(v).replace(Ext.data.Types.stripRe, ''), 10) : (this.useNull ? null : 0);
            },
            sortType: st.none,
            type: 'int'
        },

        /**
         * @property {Object} FLOAT
         * This data type means that the raw data is converted into a number before it is placed into a Record.
         * <p>The synonym <code>NUMBER</code> is equivalent.</p>
         */
        FLOAT: {
            convert: function(v) {
                return v !== undefined && v !== null && v !== '' ?
                    parseFloat(String(v).replace(Ext.data.Types.stripRe, ''), 10) : (this.useNull ? null : 0);
            },
            sortType: st.none,
            type: 'float'
        },

        /**
         * @property {Object} BOOL
         * <p>This data type means that the raw data is converted into a boolean before it is placed into
         * a Record. The string "true" and the number 1 are converted to boolean <code>true</code>.</p>
         * <p>The synonym <code>BOOLEAN</code> is equivalent.</p>
         */
        BOOL: {
            convert: function(v) {
                if (this.useNull && (v === undefined || v === null || v === '')) {
                    return null;
                }
                return v === true || v === 'true' || v == 1;
            },
            sortType: st.none,
            type: 'bool'
        },

        /**
         * @property {Object} DATE
         * This data type means that the raw data is converted into a Date before it is placed into a Record.
         * The date format is specified in the constructor of the {@link Ext.data.Field} to which this type is
         * being applied.
         */
        DATE: {
            convert: function(v) {
                var df = this.dateFormat,
                    parsed;

                if (!v) {
                    return null;
                }
                if (Ext.isDate(v)) {
                    return v;
                }
                if (df) {
                    if (df == 'timestamp') {
                        return new Date(v*1000);
                    }
                    if (df == 'time') {
                        return new Date(parseInt(v, 10));
                    }
                    return Ext.Date.parse(v, df);
                }

                parsed = Date.parse(v);
                return parsed ? new Date(parsed) : null;
            },
            sortType: st.asDate,
            type: 'date'
        }
    });

    Ext.apply(Ext.data.Types, {
        /**
         * @property {Object} BOOLEAN
         * <p>This data type means that the raw data is converted into a boolean before it is placed into
         * a Record. The string "true" and the number 1 are converted to boolean <code>true</code>.</p>
         * <p>The synonym <code>BOOL</code> is equivalent.</p>
         */
        BOOLEAN: this.BOOL,

        /**
         * @property {Object} INTEGER
         * This data type means that the raw data is converted into an integer before it is placed into a Record.
         * <p>The synonym <code>INT</code> is equivalent.</p>
         */
        INTEGER: this.INT,

        /**
         * @property {Object} NUMBER
         * This data type means that the raw data is converted into a number before it is placed into a Record.
         * <p>The synonym <code>FLOAT</code> is equivalent.</p>
         */
        NUMBER: this.FLOAT
    });
});